This is an opportunity for an entrepreneur to create a censorship-resistant platform, though, I don't know how you do it profitably when CSAM and other potentially criminal content needs to be reviewed.
These conservative groups aren't pressuring Steam and Itch directly, they're targeting payment processors. I don't think it's realistically viable to compete with Steam (or Itch) without access to Mastercard and Visa. (For anyone thinking crypto: we have a different idea of what it means to be either "realistically viable" or to "compete with Steam")
They could not allow those games to be sold through those particular payment processors and require wire transfers instead. More cumbersome payment method, but better than outright banning them.
If the payment processors try to dictate what content these sites may host even when it involves competing processors that sounds quite anti-competitive practice.