What's even a bigger concern nowadays is - for many multiplayer games you don't even need to own them...
There are tons of multiplayer games via Steam people play without ever spending a dime. That's why it's even harder to battle script kiddos. The only thing they pay for is a subscription for a cheat.
Free games, free accounts. And even when they ban your hardware, they just use hardware spoofers and go a circle. New Steam account, new MS account. Here we go again.
It takes 5min to google specific websites. Y'all know what I'm talking about.
The problems are Steam "workarounds". And especially with this, it's remarkably hard to root out cheaters from multiplayer games sadly. A better anti-cheat system will definitely help (to faster recognize a cheat and ban the player asap), but it needs to be constantly maintained - the same way cheats keep getting maintained (updated).