This is certainly true for client-side anti-cheat, but there's little reason server-side anti-cheat can't work just as well. They've been incredibly successful

This is certainly true for client-side anti-cheat, but there's little reason server-side anti-cheat can't work just as well. They've been incredibly successful in chess and (from what I've heard) virtual cycling. These are generally based on statistics and while they can't catch the very subtle cheaters those generally aren't a problem outside of actual tournaments.