Hey, just wanted to give my condolences for not being able to get the game on Steam.
The fact that Steam put the kibosh on the release while Patreon doesn't seem to have any problem with it kinda tells the same story I've been hearing from a lot of developers: Whether you can get a NSFW game on Steam REALLY depends on which curator gets assigned to interpret the rules in your individual case. For example, I know that Monolith Bay (also on Itch) has tried to get on Steam multiple times, and failed - and with that game's content, I see even less of a potential conflict with Steam's NSFW rules.
There's also the issue of Steam curators being willing to work closely with bigger developers to get their game conforming to Steam rules while smaller developers just get told outright that their game is banned. So while it's probably a massive let-down for you, perhaps you can take some comfort in the fact that you're in good company, at least.
Anyways, if you're looking for additional (mainstream) stores to sell the game on, I'd suggest trying GOG. They can be hard to work with sometimes, but they've opened up to adult games recently and from what I'm hearing, they're way more open to all kinds of content.