One misconception I see that continues to exist is that Zone only traps 3 Steel types in OU. This is simply not the case as Zone can threaten or at least force certain plays from ALL steel types bar Tran in OU.
I will be using the Air Balloon Iron Defense 3 Attacks Zone as an example as I have the most experience using that set and is the most potent imho.
1) The 3 mons Corvi, Ferro and Skarm are already obvious so let's move on.
2) Melmetal - Zone always outspeeds and gets 2 IDs up before Melly can hit it with EQ which it survives at that point and then kills with Press. Melly is hopeless in this situation as even Superpower is not enough. Choiced sets have it even rougher as locking into any of DIB, T Punch, Ice Punch is a death sentence.
3) Kartana - Kart is a Steel that doesn't fear Zone at all as it outspeeds and straight up kill Zone but this is an example of Zone influencing and forcing certain plays.
A very common set Kart runs is Scarfed and that set is used to revenge kill and threaten offensively right? But it really struggles to do that when Zone is in the back. Kart is stuck in a catch 22 situation where clicking anything besides Sacred Sword is instant death.
A very common example is Lele + Zone, You simply won't dream of clicking Sacred Sword vs Lele. Thus, even your offensive check to opposing offense, that is able to straight up kill it's the potential trapper, has to play awkwardly due to the possibility of being trapped.
4) Bisharp - Bisharp has to be at +2 boosting Item Knock to kill Zone, Zone can even hard switch into Knock and then take the followed up weakened Knock and kill it straight up with Press. Even if you don't hard switch Zone on Bish, it is forced to either die or always be at +2 when killing something. That also means you can defog in peace.
5) Exca - Exca actually does get
killed from 73%. Sand is already in a pretty bad spot as is and your sand sweeper having to wait around for Zone to lose it's Balloon before it can come in is not helping matters. This combined with the 3 originally mentioned mons and Bish also means that Zone has a significant impact on the Hazard game, trapping 2 Spikers, the best defogger, the best Spinner and the Defog punisher.
6) Scizor - Ok this one is my favorite example because this showes why trapping is ridiculous. Initially Scizor ran SD Knock BP Roost but then everyone realised that, "Shit we lose to Zone with this." And switched out SD for Uturn which is so much more passive and non threatening. This should have been bad enough on it's own but the story doesn't end there, no. Zone STILL effectively ruins Scizor as it always outspeeds Bulky Scizors and forces it to take 35%-40% with Tbolt before Uturn. You just can't stay in and Roost spam due to the threat of Iron Defense Press doing 60% on the Uturn.
You know what a 65% Scizor is in range of? 2HKO by Specs Psychic from Lele and Specs Ice Beam from Kyurem is a roll. It fails at the one job it is supposed to do despite running Uturn specifically to get away from Zone.
See? These examples illustrate how Zone can be frustrating for nearly all Steel types save Tran. You don't simply look at if it can kill the Steel in a 1v1. It affects the very way they need to be played even if they do actually beat Zone and force awkward plays.
Another thing I saw was calling it a 50/50 where Zone user wins if they get the double right but they lose if they get wrong. This is way too straight forward and an incorrect explanation of how things go down.
A free double switch into Chomp or Tran simply doesn't win you the game. So getting it wrong as a Zone user once or twice is not the end of the world. On the other hand, just getting the double switch right once for Zone is a guaranteed trap so the problem is that the 50/50 is much more skewed in the favour of the Zone user with better returns.
Lastly, Fire Spin, Whirlpool etc. Are not broken because YOU can control what gets trapped. It is not an automatic effect with an ability. The very uncompetitive nature of trapping is out of the windows for these when your counters can't be singled out forcefully. Teams are also loaded with Pivot moves nowadays so they are actually pretty bad instead of being broken. It works mostly when you are caught off guard by Pex or Bro using Block or something and by Fini because he is the Goat.
Magma Tran is a whole another beast entirely.
I will be using the Air Balloon Iron Defense 3 Attacks Zone as an example as I have the most experience using that set and is the most potent imho.
1) The 3 mons Corvi, Ferro and Skarm are already obvious so let's move on.
2) Melmetal - Zone always outspeeds and gets 2 IDs up before Melly can hit it with EQ which it survives at that point and then kills with Press. Melly is hopeless in this situation as even Superpower is not enough. Choiced sets have it even rougher as locking into any of DIB, T Punch, Ice Punch is a death sentence.
3) Kartana - Kart is a Steel that doesn't fear Zone at all as it outspeeds and straight up kill Zone but this is an example of Zone influencing and forcing certain plays.
A very common set Kart runs is Scarfed and that set is used to revenge kill and threaten offensively right? But it really struggles to do that when Zone is in the back. Kart is stuck in a catch 22 situation where clicking anything besides Sacred Sword is instant death.
A very common example is Lele + Zone, You simply won't dream of clicking Sacred Sword vs Lele. Thus, even your offensive check to opposing offense, that is able to straight up kill it's the potential trapper, has to play awkwardly due to the possibility of being trapped.
4) Bisharp - Bisharp has to be at +2 boosting Item Knock to kill Zone, Zone can even hard switch into Knock and then take the followed up weakened Knock and kill it straight up with Press. Even if you don't hard switch Zone on Bish, it is forced to either die or always be at +2 when killing something. That also means you can defog in peace.
5) Exca - Exca actually does get
killed from 73%. Sand is already in a pretty bad spot as is and your sand sweeper having to wait around for Zone to lose it's Balloon before it can come in is not helping matters. This combined with the 3 originally mentioned mons and Bish also means that Zone has a significant impact on the Hazard game, trapping 2 Spikers, the best defogger, the best Spinner and the Defog punisher.
6) Scizor - Ok this one is my favorite example because this showes why trapping is ridiculous. Initially Scizor ran SD Knock BP Roost but then everyone realised that, "Shit we lose to Zone with this." And switched out SD for Uturn which is so much more passive and non threatening. This should have been bad enough on it's own but the story doesn't end there, no. Zone STILL effectively ruins Scizor as it always outspeeds Bulky Scizors and forces it to take 35%-40% with Tbolt before Uturn. You just can't stay in and Roost spam due to the threat of Iron Defense Press doing 60% on the Uturn.
You know what a 65% Scizor is in range of? 2HKO by Specs Psychic from Lele and Specs Ice Beam from Kyurem is a roll. It fails at the one job it is supposed to do despite running Uturn specifically to get away from Zone.
See? These examples illustrate how Zone can be frustrating for nearly all Steel types save Tran. You don't simply look at if it can kill the Steel in a 1v1. It affects the very way they need to be played even if they do actually beat Zone and force awkward plays.
Another thing I saw was calling it a 50/50 where Zone user wins if they get the double right but they lose if they get wrong. This is way too straight forward and an incorrect explanation of how things go down.
A free double switch into Chomp or Tran simply doesn't win you the game. So getting it wrong as a Zone user once or twice is not the end of the world. On the other hand, just getting the double switch right once for Zone is a guaranteed trap so the problem is that the 50/50 is much more skewed in the favour of the Zone user with better returns.
Lastly, Fire Spin, Whirlpool etc. Are not broken because YOU can control what gets trapped. It is not an automatic effect with an ability. The very uncompetitive nature of trapping is out of the windows for these when your counters can't be singled out forcefully. Teams are also loaded with Pivot moves nowadays so they are actually pretty bad instead of being broken. It works mostly when you are caught off guard by Pex or Bro using Block or something and by Fini because he is the Goat.
Magma Tran is a whole another beast entirely.