I'd use YouTube and other methods to promote. I've read about itch and I don't think it's the best platform for full visibility, although if I finish it properly it will be uploaded to itch.
If you really don't think steam is a good fit, that's okay, I'm not going to critique your opinion of steam. What I might ask is—on any platform, is the core idea good enough for a full game release with several more months of work?