While valve is indeed quite neglectful, the reason they're "behind" on anticheats is because they don't run extremely invasive ones like EAC (Easy Anti-Cheat) or Vanguard (what Valorant uses). These operate exactly like malware/rootkits that you just have to trust. Blegh. Even if I wanted to run those (I do not), they don't work on linux anyways.
So I'll stick to cs:go and tf2 community servers, thanks.