Counterpoint, play any game without anticheat and realize just how much worse it can be. (and before someone says it, custom servers with dedicated admins doesn't scale and tends to cause lots of petty drama)
It does stop some classes of hacks, ups the effort considerably as you hack needs to be in kernel or with hardware. But its pretty much impossible to stop on x86/windows PCs.
And CS is completely overrun with cheaters. I don't play Dota like games but afaik they all have effective obfuscation, so ESP/wallhack like cheats aren't effective. But they have some auto aim cheats for abilities.
Everybody is "doing something". It's a question of what is something. Account-banning people after proven cheating is also something. I would imagine a competitive game with a skill-based match-making, especially a successful one can do that.
Asking people to swear to not cheat in ToS is also something. Only installing the game on the proper trusted computing or doing server-side anticheat is something too.
The issue is with the company deciding to disregard customers concerns about security and privacy to get this something for cheap from a third-party vendor.
If we must pick just one problem I'd say it's that the techniques that we develop for anti cheat will later be used by authoritarian regimes to turn our devices into weapons against those of us foolish enough to dissent.
all it really does in practice is produce a market for paid cheats.
if it's a pain in the ass to stay ahead of the anti-cheats, then people with the skills to do so will expect (and receive) payment from those wishing to cheat.
The worst case scenario is the TF2 catbot scenario, which anticheat seems to stop.