I think OP is saying someone should make a platform that hasn't lost marbles and would allow this content, but you would still want to block CSAM and that is not easy to do.
Itch hasn't lost its marbles, they're forced to remove this content by payment processors. They're critical infrastructure, they shouldn't be allowed to arbitrate on behalf of an entire society. We need laws to require them to carry payments for any legal transaction. Paying for porn games is legal.
I think the implication with saying "a company that hasn't lost its marbles" is that Itch and Steam have lost their marbles. You can argue that Steam should have pushed back, but Itch definitely lacks the leverage to refuse here.