When people make this argument generally though they are usually talking about the slippery slopes.absolutely, anyone who argues against complex bans because
For example basically unban all of Ubers and make them usable in OU as long as they are limited to level 50 or something. Simple enough right? But what if people wanted to use their ubers at level 100? Then you might have to start limiting items they can use. You might even start restricting moves they can use , might start restricting Evs and IVs to keep things balanced. And you have to do this for every single pokemon. And this is where it can start to lose accessibility among newer players. You could end up with a situation where you can use move X on your level 100 giritania, but only with Evs and IVs Y, and Z. Etc and so on, for every single mon. And this can be hard to keep track of for a completely novice player coming to Smogon. And eventually the tiering principles we have used to date fall apart as well. Versus using complex bans very sparingly ( and preferably not at all ) and having a simple banlist is simply and easy to follow for everyone and most importantly isn't as arbitrary as customizing every pokemon to fit in a given competitive tier, allows pokemon to be played at their full power and respects the fact that some pokemon are simply better than others and they should be allowed to play with their peers and not be forcibly nerfed to be balanced for play in a tier it doesn't belong.