I think the point about wallhack being more common in higher elo is more likely. I would add that some forms of trigger botting and recoil control cheats are actually more difficult to tell than wallhacking. Spinbotters don't get very high elo because they get mass reported because of how blatant they are, likely not due to VAC. I would need some real evidence to believe that claim (although as I said I similarly have no evidence myself to convince you to accept my claim).
One thing I can say is that I do frequently meet cheaters in CS these days, and the issue has gotten so bad in my experience that many cheaters even announce at the start of the game that they eg. have wallhack. Or one team member will turn on cheats if a game is getting close towards the end of the game. Also, the main reason FACEIT exists is for its anti-cheat, and on FACEIT there are almost no reports of cheating, and it's a big deal when it happens. If VAC was really working now we would see more people leaving FACEIT. I must ask when you started playing CS? Because the only way your post makes sense to me is if you started playing around the time when CS2 came out, which indeed did have more cheaters then it does now, but that was truly an exceptional level of cheating and I don't think that is a fair point of comparison, especially as a comparison to Vanguard.
I admit to taking claims about Vanguard at face value and I've never played Valorant (in part due to Vanguard, as I don't want to install a rootkit). But what you say about Vanguard also completely goes against what I have heard about it.