The true problem with TTRPGs is that there are both far too many of them and they are all far too hard to discover, but also, even if you know where to look and how to look for them, the signal-to-noise ratio is horrendous.

Like say you want a mech RPG that isn't Lancer. You go looking on itchio and you're going to find a bunch of obnoxious, faggy solo journaling games about toxic yuri pilots having sex with their mechs, and also the "game" itself is just flipping cards and then writing about the mech sex, based on the somehow acclaimed solo journaling toxic yuri system that is beloved by a large number of itchio pseudo-designers, so now there's dozens of these fucking things clogging up the results of any search, because they do a weekly game jam, somehow.

There are sites like RPG geek, but they do such a terrible job actually cataloging games that you're not going to have a much better time finding anything there, and even if you do, the actual information on the game will be sparse, and there will be no reviews, no website, nothing. Also the game will be out of print or otherwise vanished from the internet because the creator crashed out 3 months ago and actually the game was never finished beyond a rough draft PDF.

I'd wager that if a hyperspecific niche system doesn't already exist, there's something else out there that is actually close enough or generic enough or homebrew-able enough to cover your needs, but the true problem is finding those systems and not falling into the trap of trying to make a whole system from scratch, with bespoke, unique mechanics, or even worse, being the kind of retard who thinks they can make D&D work as the basis for their hyper niche game idea.