i played CS competitively and the cheating was horrendous. if i had to put a number to it, i would guess that 50% were cheating in some form simply because it wasn't very difficult. I would ultimately be relying on checking the number of digits in your Steam ID to tell whether this account was fresh (higher probability that you bought a new one and were cheating). I think the anon matchmaking is the horrible part, not the anti cheat software.
i disagree. Faceit and others have really done a great job. Riot's anticheat is also fairly effective. Anyway, it all depends on what you're trying to achieve. If it's casual gameplay, then who cares (although I wouldn't want to play in a server with cheaters even casually). But if you have ranks and a competitive scene, then anticheat is crucial