What results of this is a metagame that is a nightmare to navigate, especially in teambuilding. Because the means of progress available to the tier are so easily negated by its presence, very strange options are forced to try and disrupt it; while this seems like a good thing on paper to encourage creative building, forcing suboptimal options is not ideal nor pallatable. However there is actually a very prominent move it forces higher usage of that creates absurd volatility in gameplay:
Tera Blast. Laugh it up, but I'm dead serious. There have been several successful teams such as Storm Zone's
Cinderace team and a surge in Sandy Shocks/Dragonite/opposing Landorus-T trying to take advantage of this move to delete Gliscor, that notably boast natural great benefits in pressuring similar Ground- and Flying-type targets. This causes the move to be used in practice more often to tech other Pokemon due to the move being on the set anyway; I cannot tell you how many times in my reqs run I've run into Water- and Ice-type Tera Blast even without a Gliscor on the team I used.
I think my main issue with tera blast ice is that Sandy Shocks loves to use tera blast ice anyways, even without Gliscor in the tier, as well as the fact that Dragonite gets ice spinner... I haven't seen tera blast ice Landorus-T yet, but I have seen tera blast ice Amoonguss.
The overall issue I have with this argument is that nobody is forcing these players to use tera blast ice. In the past, we have used stuff like tera blast fighting for Kingambit on stuff like assault vest Toxapex, specs Dragapult, Zapdos, and shell smash Polteageist. Now, it is reasonable to argue that Kingambit is broken in itself, but there are cases where mons use tera blast for non-broken mons, such as tera blast ground Iron Moth for Heatran and tera blast fire Breloom for Corviknight (and Gholdengo). There are other options, but these are just to name a few.
The point I want to make is that you really can run tera blast to just one shot whatever you want if you really wanted to, but you don't need to. There are other checks and counters to Gliscor, such as Hatterene, Corviknight, taunt, setup, and substitute, that do not require terastallization. It is fine to adapt and try to resolve a weakness with tera blast as a move, which is what a small amount of teams end up doing, but it is often because it is used in conjunction with a team that is incredibly powerful against other teams without the desired target in the picture.
Now, as to the other argument, as to that Gliscor has lots of tools at its disposal and can adapt to its counters:
However, it's the things it can do with its resilience into progress that push it to an egregious extent. Entering Generation 9 it obtained both Toxic Spikes and Spikes, and it's obviously excellent at using them. This is thanks to how well it can take advantage of passive gamestates that occur more frequently thanks to its resilience into status/Knock Off, but this doesn't give the full picture about why it deserves priority in evaluation over Gholdengo imo. Aside from its ability to efficiently stack hazards, we have seen a truly obscene amount of set permutations that take advantage of its access to Swords Dance, Knock Off, Toxic, U-turn, and Taunt in order to diversify its style of pressure and punish attempts to respond to it, including mirrors. While hazards can complement these tools, Gliscor is able to use these tools independently to create progress or take advantage of the gamestates it can force, all while being able to seamlessly adapt to conventional means of counterplay.
Ignoring the fact that options like toxic spikes and taunt are underused, I can see these moves rising in usage to deal with opposing Gliscor and Corviknight.
There are even cases where one might argue that Magnezone could also be used if Corviknight rises in usage as a way to touch on the idea of adaptation, but we'll get to that at a later point.
Let's say I am building a team with Gliscor, and let's say I want this to be a hazard setter. I would lock in protect and spikes, and then I have the options of toxic, earthquake, and knock off. Each have their own benefits, and this already does cause a problem for the Gliscor player in what moves to choose. Do I choose toxic in order to punish Great Tusk? Do I choose knock off to force progress? Do I choose earthquake for consistent damage?
Now, let's add the other move in question: taunt (Yes, toxic spikes exists, but I want to touch on that in a later argument).
Here, the situation is made even more extreme with taunt in the picture. If I pick toxic and taunt, options like poison types and Hatterene can switch in freely, Hatterene even switching in with zero repercussions. If I pick taunt and knock off, I can get spun on by Great Tusk easily, and Hatterene can still choose to switch in despite losing its item and argue that long term, the damage is minimal and is healable with draining kiss (or can use Gliscor as an entry point for a setup). Lastly, taunt and earthquake is an option, and it still struggles against Great Tusk and Hatterene, the latter of which even gets to keep the leftovers.
In addition to the argument of taunt not being able to get through all hazard removal (and especially not Hatterene), there are still, again, the checks that I mentioned earlier in taunt, substitute, and setup.
I didn't even mention the consequences of relying on taunt; let's say I have 2 defoggers in Corviknight and Mandibuzz/Weezing-Galar/Scizor/Talonflame. In the case of Corviknight + Mandibuzz or Talonflame, Gliscor specifically needs taunt + toxic. In the case of Corviknight and Scizor or neutralizing gas Weezing-Galar, Gliscor specifically needs taunt and earthquake or taunt + knock off. Lastly, in the case of Corviknight and levitate Weezing-Galar, the worst Gliscor can do is remove items. Let's say it removes boots in this scenario, for example; Gliscor still wouldn't be able to force progress because both of these defoggers because they bypass spikes.
Now, I know team structures like balance and offense cannot rely on multiple defoggers, but these teams can still run Great Tusk + Hatterene (an anti-hazard core that historically has been pretty solid in OU), pivots carrying taunt, setup sweepers with pivot support, or, in the case of balance, boots spam (Let's be real, balance used boots spam during the HOME meta as well, it's not like Gliscor restrictively manipulates teambuilding by forcing all the boots on).
Alright, let's go back to Magnezone, because I think this could be an option that people could argue:
By running Magnezone, Gliscor is pretty much obligated to run knock off in order to remove potential shed shells. I think it's safe to make that assumption, because otherwise, it would need to run taunt to beat shed shell Corviknight and, well, we go full circle (also, why would you even bother running a Magnezone in that case?).
Now, this means that Gliscor does not need to run taunt, but the scenario still applies; do you choose to lose to Great Tusk and certain knock absorbers without toxic, or do you yield your rights to punishing Hatterene (and niche options like neutralizing gas Weezing-Galar) without earthquake? This is, despite losing your option of Corviknight, still a lot more predictable and easy to manage because the opposing Gliscor has to use 3 moves; protect, knock off, and spikes.
Okay, it's time for the toxic spikes argument:
Toxic spikes play out INCREDIBLY similar to spikes, except that if the opponent is toxic + toxic spikes, you cannot use Great Tusk
oh wait, it's the same as if it was using toxic + spikes in the first place. You don't even need to use a poison type to absorb it, except now you could throw in a couple predictions with your poison type if you REALLY wanted to.
Now, it is time to address the elephant in the room (tera ghost):
In a previous post, I mentioned that Ting-Lu could do something similar and emulate hazard stack with tera ghost, and I'm willing to acknowledge that Gliscor can do the same. However, the main difference with this is that if Gliscor terastallizes ghost, you have even MORE options to punish it, such as with your own hazards to match (or even outdamage) the healing of poison heal + protect.
Furthermore, I want to talk about the fact that different team structures do well into Gliscor anyways. Take magic guard Clefable + hazard resilient options (whether it be heavy duty boots or non-grounded mons that don't care about rocks that much), and you get a solid team structure in general to deal with Gliscor. Take grass spam teams, where the sheer power can break through the hazard stacking core and the grassy terrain allows the teammates to regain some of the HP they lose from hazards (hazards in general are less impactful against offensive teams; the games are faster paced and therefore, hazards don't get as many opportunities to deal the chip damage). These are just some examples that can deal with Gliscor decently.
Lastly, I wanted to talk about some of the positive impacts that Gliscor can do on the tier, even if others argue that it has some bad impacts.
For bulkier offense teams, a pivot set could be used to essentially get a bulky pivot that is a lot more reusable than other options such as Landorus-T. This could be bringing in powerful attackers over and over again, which I think is a really nice dynamic.
For more balanced teams, it can serve as a hazard resilient knock absorber, allowing for Gliscor to help balance teams to deal with menacing physical knockers such as Great Tusk, physical Iron Valiant, some variants of Rillaboom (or all choice band variants if you scout it with another protect mon), and more fringe, unique options such as Meowscarada, Ogerpon-Cornerstone, Ogerpon (base), and Scizor.
For teams closer to semi-stall and stall, Gliscor can serve as either a bulky win condition or as a way to force some progress with knock off and toxic (which I think can be a healthy thing).
Lastly, Gliscor does serve as, finally, another option to deal with volt switchers such as Zapdos. There have been relatively few options for dealing with Zapdos in the HOME metagame, and Gliscor is an option that is quite splashable; Clodsire was hard to fit on most teams and Ting-Lu could eventually get worn down depending on your set.