All the input verification and processing of player locations is done on the server (at least in any respectable game), I can smell the fact that you haven’t touched a single line of multiplayer code in your life from here

Those checks can be buggy ofc or do not cover all possible exploitable behaviors. But when there are implemented correctly you can not circumvent them. Similar to a Login form, bugs excist.

A youtuber named CodeOverflow made two great series about game exploitation.

EDIT: things like physical hardware hacks are also near impossible to detect reliably except for stuff like blatant recoil hacks

Not talking about that. And Client side anti cheat does also not help here.