@IlIlIIllIlIlIl Can't get on board with this. I am a Caustic main, so I'm bound to appear biased here, but that is literally all he's got. That IS his power. He can chuck gas traps around to annoy people, defend areas, push teams, create barriers, etc.
Don't get me wrong, at times he seems like the single best legend to have in some scenarios. Me? I use him because everyone on PS4 cheats and uses aim assisted M&K now, so I have to utilise defence to slow down fights and stand a chance against the no-lifers, and it works - he is the best one for me. But then, if you look at the wider picture, so is Pathfinder. So is Wraith. Hell, so is Crypto. They all have something going for them and I almost always say to myself "*, I wish I was Pathfinder for this final ring" etc, and personally, this particular situation you've described has happened to me perhaps once this year. It may feel overpowering when it happens to you, but really, when does it actually happen? Does it happen more than Wraith being able to withstand final ring damage? Or more often than Gibby having an ult that essentially wins final circles on its own, whilst also having three forms of damage reduction at his disposal?
If you're holed up in a building, there has to be a way to force you to change position. The game would be bs otherwise. It'd become Call of Duty, everyone would camp. But they don't because it's very hard to do so in Apex due to map design, mechanics, and legend abilities.
Tl;Dr, for me, he works exactly as intended, and comes with his own weaknesses and counters just like everyone else. For example, another Caustic.