While VAC is indeed far from competent at detecting all but the most rudimentary cheats, it is so by design. When the first third party CSGO matchmaking/league services decided to use kernel level AC, Valve publically said they would personally not do such a thing. I can't remember if any exact reasons were named at the time, but I do think it's a fair take on their end. It's not like they're locking developers into using VAC anyway.
Furthermore, more recently they have debuted VACNet, which uses machine learning, most likely to recognize certain patterns and behaviors associated with cheating. Probably still avoidable if one were to use subtle settings and knows how to act properly. But it shows they haven't given up and are trying to explore alternative methods at least. I'm admittedly not familiar with how successful it has been as I have not been playing or even following the game for a long time.
Furthermore, more recently they have debuted VACNet, which uses machine learning, most likely to recognize certain patterns and behaviors associated with cheating. Probably still avoidable if one were to use subtle settings and knows how to act properly. But it shows they haven't given up and are trying to explore alternative methods at least. I'm admittedly not familiar with how successful it has been as I have not been playing or even following the game for a long time.