Steam is 'an unsafe place for teens and young adults': US senator warns Gabe Newell of 'more intense scrutiny' from the government if Valve doesn't take action against extremist content
Honestly, this seams a bit unfair. My understanding is that VAC is free or very inexpensive and pretty decent, while other options are potentially better for some cases and more expensive. Valve making a reasonable anti-cheat available is a good thing IMO.
So it existing is a good thing, it just may be the wrong fit for a given game (e.g. more popular games probably need a more intense anti-cheat).
If a game isn't detecting cheaters well enough, blame the game, not the anti-cheat system it uses.