i think ppl underestimate the work of validating game submissions to steam (doesn't mean valve couldn't afford it), but it's mostly a matter of valve not wanting to take responsibility of what gets on steam. they don't want to create a ruleset and be specific of what's allowed in and what's not cos that would make them accountable and they most definitely don't want any of that
i'm sure valve's algorithms are super impressive, i can't imagine their algorithms wouldn't be able to detect the word "rape" in the title of the game, so it's not wild to assume the algorithms are set up deliberately to not looking for that. my guess is that they're looking for copyrighted material, or repeats of games already uploaded, the kinds of things that would get valve in trouble like someone uploading a pirated copy of assassins creed, idk.
the filtering of the vile and hateful games is outsourced to the community then, leaving it to us to decide what's too offensive to belong on the store. kind of like reverse greenlight i guess. rape sim 2019 will likely get removed but it seems as not enough of the community is too offended by those hentai puzzles so they'll stay. i could see bigger publishers also pushing valve to remove those kinds of games cos it just looks bad to be sitting next to a game called rape sim 2019, but considering the 8chan thing thq nordic just pulled, who the fuck knows lol
hiring a validation team would probably not be cheap, but i think it would mostly be difficult for valve cos it would require them to have a real ruleset rather than "straight up trolling" and that costs them money. cos for all the time rape sim 2019 will be offered in the store before being taken down valve will profit of it just fine. and that can't be fixed with algorithms either, it's valve that needs fixing in that respect (or maybe they'll just get sued for selling yet another game about killing queers, lord zeus knows they deserve it)