If cheaters were capped to mimicking good players, that's already an incredible win over the status quo. The players that are walling (as an example), are playing with more information than they should and this should always be detectable with enough observation, especially in terms of them displaying super-human reaction times and being pre-positioned to their advantage... so I'm not quite as pessimistic as you are about this not having good returns.

I'm sure there's a reason why they don't, but I wonder why games don't try implementing honey pots, like rendering a fake player behind a wall and automatically banning if a player's crosshair snaps onto them, etc.