That doesn’t stop a client from rotating walls so they get culled and don’t appear,

You're talking about FPS games, a subset of competitive games. This, and the other things you've brought up aren't a problem for other types of games.

Most types of RTS and 2D fighting games will not have any of the problems you've listed.

But for FPS games specifically, the server should not report player location unless the player is visible. If people elsewhere in this thread are right, the server already does this with ray tracing. Not the fancy lighting stuff, just the basic "draw a line and see if X is hit" stuff.

And most FPS games will already have that logic built in, as they tend to use ray tracing for bullet hit detection, often referred to as 'hitscan'.

So no amount of wall invisibility will have an effect.

or modifying shaders to outline enemies,

IMO the game should give all players the ability to turn on outlines for enemies/teammates anyways. People who have difficulties parsing colors should have that as an accessibility option.

Marvel Rivals already does this, and allows the player to choose the color that most stands out to them.

or using coordinate data to run a map/radar

Not a problem if the server doesn't report player locations unless they're visibly.

and auto aim bot.

This one is admittedly a little harder, but again not impossible to deal with. Chess sites already do this with ELO tracking and matching moves against the best possible move.

If on Wednesday you're playing like an ELO 600, and Thursday you're suddenly playing like an ELO 3200, you're cheating. In an FPS that would look like going from an accuracy of 12% to an accuracy of 100%.

Most of the time I think you can let the community self police, but for competitive play you probably can’t stop all forms of cheating.

Sure, but instead of being passive and using kernel level spyware like most AAA studios like to do, doing the basic sever side authority checks are far more effective.

That chess guy used a remote controlled butt plug to cheat, people will always find a way.

And he was caught. Do you think we should be checking every chess grandmasters butthole going forward?