I wish to provide with an outline on swagger's impact on the general metagame, by addressing the inherent qualities of the move, underlining its unique and intricate qualities that make it stand out from other status moves in the game.
(I swear this is serious. Please don't delete this)
SWAGGER is uncompetitive
(But it's fucking funny)
First off, if you use Swagger you are either one of two people: someone who enjoys to see people suffer while living in your parents' basement or an absolute gangster.
Think about it. You're willing to put your reputation as a competent player on the line and at the hands of random number generated from some CAM-PU-TOR MA-CHINE just to assert dominance. And by increasing your opponent's Pokémon's attack, you're essentially playing Russian roulette, proving you give absolutely no fucks. That's a power move if I've ever seen one.
There isn't a soul on this Earth who could sit down and explain to me why it's a good thing that such a move exists. Whoever came up with it probably endorses anarchy and should be locked up in a psychiatric ward.
But there are some
people that have found a lot of success manipulating RNG or playing the odds, and
though this kind of strategy isn't something I'd recommend all the time what I can say is that...
Most of the time, some of the time
IT WORKS EVERY DAMM TIME
So we've discussed how it's not a move that any sane being would ever use and that it's really frustrating and distracting, because if it wasn't clear
you essentially are forcing your opponent to play a game of hot potato with themselves as they nervously switch from one Pokémon to another, then stop when they think can stay in and survive a turn... maybe switch a second time, "CURSE WITH SNORLAX BABY!!! ...
Shit"
But we have to stop for a moment and think. Can a move that doesn't even always work all the time be so threatening?
On paper we know it has around 95% accuracy. It means 5 out of 100 you are contributing as much to the game as much as Ash's father contributed to his son's college tuition.
(Also I might be wrong about this part but Swagger might also be one of those "100% totally guaranteed secondary effect moves" that actually have a 1/256 odds of not even working, like Dynamic Punch)
So factoring confusion chance of the opponent hitting itself, which if I'm not mistaken is 50%, the move seems strong but already a little bit inconsistent.
But these odds are based on the premise that you're actually willing to and can afford to click the move. There are other inconsistencies that only apply to this move alone and do not apply to other status moves like sleep powder, spore, confuse ray, thunder wave:
What happens if they switch?
You are now back to square 1 and are exposing yourself to the risk of getting knocked the hell out should you choose to click the status move again. But this is part of the risk and I suppose this is also what make it fun, in my opinion.
What if they have a physical attacker?
Tough shit, my dude. You're the one who decided to gamble away your reputation (I wonder if that applies to all players here???
).
What happens if the opponent's Pokemon's attack is already maxed out?
Then the move will straight up not work, unlike confuse ray. This in my opinion is where Swagger really shows its true filth as a move because in GSC Pokemon can reach the 999 cap of their attack way earlier than 6 stages of stats, meaning you can click swagger AT MOST 3 TIMES.
What if my girlfriend left me *WHEEZE*?
She's right for having done so.
If you're looking for shits and giggles then you don't have to read further.
But now, in all seriousness, if you're trying to find consistency, or at least to exploit specific weaknesses in an opponent's style then you can find success with swagger against these threats, ranked in descending order of magnitude
1
Stall pokemon

:missy:
The general passive nature of stall builds means that there are plenty of opportunities to stack confusion and attack boosts on your opponent with little drawback. This has the potential to completely invalidate key Pokémon that are the makeup of crucial defensive cores, opening up windows of opportunity that would otherwise not be present with other status moves. The only other status that comes close to these levels of power is paralysis, and though the competitive community do tend to see paralysis as a more competitive move, it's not nearly as polarising or accessible.
2
Special attackers
More often than not, if you have a Pokemon with Swagger, then these Pokemon will be the primary target you are searching for, ie. Pokemon that do not have access or have revealed not to possess powerful physical stab or coverage moves like Double Edge, Earthquake etc. The reason is because if you land the move swagger and they decide to stay in, the only downside now is if they manage to hit you through the chances of confusion since special attackers hurt you using their special attack and have only to lose from the increased attack. Also these Pokemon are quite consistently frail on the physical end so this hurts them more than any other target.
3 Snorlax

The big boy gets his own category because it's the strongest non in the game and even the slight chance of taking it out is highly beneficial. The high damage to itself really opens up many windows of opportunity to pick apart a team, especially when out up against the likes of your Zapdos, which should be able to take Snorlax out in three swift blows of Thunder/Thunderbolt. Do not underestimate the value of Snorlax missing a turn to do anything.
3.5 other physical attackers/mixed attackers

This encompasses a group of undesirable/dangerous targets. While taking them out would certainly benefit your team, it factors in some risks that are way too high for you to want to find a confusion on them in most games, for obvious reasons. But when you take these guys out you get to celebrate.
4 odd support Pokemon/4mss victims

This is already a lot less beneficial but there are chances where you can target these Pokemon if you have nothing better to click.
I can see many scenarios where a flying Pokemon clicks this move on grounded Pokemon like steelix or golem to annoy them, but they also have a lot of bulk so it will more annoy them than hurt them.
Conclusion
Of all the rng moves this one is probably the least consistent. On one end it would sadden me to see this move gone, because it can be fun. However,
I am not opposed to it being banned (there is a part that wants it gone) not because of the generally frustrating nature of the move, but due to how it is so polarising and
has the ability to completely stall break with little to no drawback. I do realise this last part sounds a little bit conceited, and that's why I encourage people to read the other posts which all have valid points. I'd like to close off by saying Swagger is far from broken but that its highly un-interactive nature and the added possibility of chipping Pokemon with additional status moves or other attacks gives potential for it to really blow things out of proportion in some cases. Since it's officially a volatile status condition, it can be polarising in a way that Paralysis and Sleep are not.
Again my point of view can be scued into one direction and I recognise its potential to sound or be misleading, but the way I have been playing with swagger in GSC lower tiers has led me to think that it can affect more defensive play styles. Stall is a defining play style of the GSC metagame and to see it get mollywhopped by a single move sucks. It can hurt consistency of certain offense teams in certain scenarios as well (like special offense heavy teams) but they typically have more tools. Swagger seems, in its unfairness, not to be evenly distributed across play styles and should a group of players decide to abuse the move, this would skew the level of competition towards an unhealthy environment that does not reflect the GSC competitive landscape. If I saw someone become champion using this, I would hope that they are equally proficient at using all the other more consistent play styles but I can't mandate that so it's just not a good move.