How? You can literally turn IPv4 off on your whole network, or selectively by device. But if you turn off your IPv4 you will get cut off of a good chunk of the internet.
And the only reason we have unused IPv4's is because a big part of the internet is behind NAT of some kind like CGNAT.
Just making it harder to cheat and having a way to patch it and instantly get a wave of bans does discourage cheating quite a bit. Especially in paid games. You will never get rid of cheating completely, but cutting down on it and discouraging it is the name of the game.
CGNAT usually only applies to the IPv4. The IPv6 prefix you get is usually public.