just wanted to note:
steam does have the option to blacklist stuff, it's just buried in the settings, so it's less of a "today i don't want this" and more like a "i don't want to see horror stuff at all"
I stand corrected.
Steam does indeed has tag exclusion. When you browse the catalog, and you narrow by tags, each tag has a - sign right to it and a check box left to it. If you tick the checkbox or click the tag, the game has to have that tag and if you click the - , the games with that tag are excluded.
I did not even know that was possible. But it has the same design flaw that would apply here. The tags have to be correct for that. And the steam catalogue only has like 140k items. So they have more resources, and less items. I am surprised we even have ability to excluce one tag here, even if that method is not known to everyone.
(What you meant is the mature content filtering. Itch has that too, but only adult, yes or no.)