We can not ban specific customs. Either we ban them entirely, or we don't ban them at all.
How do you decide what is ban-worthy or not?
There's no clear ruleset. Every player has a different opinion on the matter. Do we only let a small, experienced group of players decide for everyone what moves we will all play with? Do we make a general vote, and let the majority decide? Unless the vast majority (almost every one, universally) agrees as to what moves to ban, we won't get anywhere, and this is not going to happen, seeing how divided the opinions on customs are. And even then;
How do you get the majority to decide exactly that Pikachu's X move is broken, along with Villager's Y move, DK's Z move and nothing else?
How do we get the majority to decide that we only ban these three moves, and that the others are fine? Banning specific moves would be a complex ban, and while great in theory or casually with friends, it would be too dificult to do in practice. It would be too complicated to ban several moves from each character to arrive to the best, most neutral and balanced metagame possible, because we don't know and probably never will agree on what is it. Why would we ban Villager's Timber Counter, but let Pikachu have his Heavy Skull Bash? Might as well ban the Skull Bash too. But then, why would we let DK have his Kong Cyclone? When do we decide that the meta is fine and when do we stop banning moves? We can't simply ban a ton of moves to balance out the meta. Also, all this is assuming the meta needs to be balanced, and to be honest, it probably doesn't. Some characters are indeed better than others, but that's part of "what makes smash smash", and even low tier characters can perform well, while high tier characters stay managable. The only reason to ban moves is if they are already breaking the meta, which is not happening.
It's harder to decide if a move is broken than it is to decide if a character/stage is broken, which is already hard itself.
Character bans only depend on MUs. If a character has a huge MU advantage against a large majority of the cast, he MIGHT get suspected for a ban. Usually, a character will do well against another character no matter what. If you repeat the same MU over and over again, you can generally see a pattern as to what character is better, if there is one, independently of who's playing.
Moves are much more situational, so it's harder to tell if they're broken or not. It does depend on the MU, but also on the situation. A lot of the time, there's ways to avoid getting hit by a move no matter how good it is. Yes Diddy's grab is dangerous, but if you keep your distance or throw hitboxes, it can't touch you. Yes Pac's key is dangerous, but if you're not on the same level as him it won't hit you. You have an additional criteria for what makes it broken, it's not solely dependent on MU. A move being good against a certain character doesn't mean it will always work against him/her.
For a move to be considered ban worthy, it has to be efficient in the majority of situations, and work against the majority of the characters. It needs to be a very high reward/no risk move that you can easily spam and get a lot of benefits from. With all the testing we've done so far, nothing even comes close to this. Even Diddy's Grab (to Dthrow to Uair) doesn't come close to this. You can't simply ban a move because ''it's annoying'' or ''it works relatively well against some characters sometimes''. It has to be game-breaking. It has to render competitive play impossible or extremely limit the choice of characters you can make.
Because of this, while it is a good idea, and while you can do that if you're playing casually, it's simply not possible or very very unlikely to happen in a competitive environment as big and as diverse as the smash scene is. At least, not now. I'm against the idea of banning specific moves as a whole.
- We cannot ban specific moves because they are broken, since there are no broken moves.
- We cannot ban specific moves to balance the meta, because it would be too difficult to arrive to a concensus.
Concerning the Timber Counter (because that's what OP mentionned), there are ways to deal with it. It doesn't make approaches impossible, it only forces you to approach by air. Pac's trampoline does the exact same thing, and no one is calling it broken. You can simply wait until it disappears, or throw projectiles. You can try to approach by air. It is a good move, and the sapling does make Villager safer, but it's not as broken as everyone claims. As for the tree: it has less HP than the other trees. You can kill it easily. Just be sure not to attack it if you're too close. Remember that Villager can Fair it if you're close to it to deal you damage. Also, with Timber Counter, Villager loses a kill move in the axe, and the tree deals less knockback. So yeah, it is a cool move, but it also has downsides.