But surely enforcement is a good thing; then it’s up to the parents to buy the game for their kids, giving them much more say
You shouldn’t need to if the parents are competent.
I think informing parents about the content of games is a good idea. Blood, violence, sexual situations, foul language, etc, this information should be available if the parent desires it. And “M” rated games (in the US anyway) should be restricted from being purchased by minors. But, we’re already doing that so, it’s all good.
Parents are the decider.
As a filmmaker says, “If I can influence your child in 90 minutes and you can’t over 18 years…”