This question already has an answer here:
I was wondering, why don't other force cultures play a larger role, especially as of Force awakens? Are there actually not other cultures, with philosophies that aren't divided light/dark? If there are, why aren't they larger influences in the galaxy? I think I recall one or two other cultures from the books, but on planets that were very isolated... but I would expect to see a lot more of them, reasonably, from all the leftover traditions that 'discovered' the force for each species and isolated planet, from religions which also have skills (like meditation, self discipline, visualization, energy work), from old superstitions that would suddenly become relevant once kids were no longer recruited by the Jedi.
The Sith and Jedi define themselves in opposition, and can't really exist without the other. They might not talk about other force philosophies, and deny middle ground, or third way out, because it lost them recruits. The answer here citing the "manual for students" suggests the Jedi temple might have recruited kids forcefully, and if they also sqooshed religions, the other cultures might slowly fade. Perhaps the empire was hunting down force users - even those who were nothing like Jedi but sorcerers/acolytes/shamans/warrior-kings of wherever. But I don't recall this happening in canon, unless I missed something. And this theory doesn't fit with what we see of the galaxy in Force Awakens.
If that were the case, I would expect a lot more showing up in Force awakens, as there's nobody left to suppress them and any talented kids who found the traditions/religions/superstitions that would let them teach themselves would have time to grow and find each other...especially if there are people who can figure out some things without prior training, as Rey seems to. Instead, we have the impression that the Force has been all but forgotten.
So after all that musing, the question I am asking is - is there a reason other Force-using cultures are not more widely represented? Especially in the last movie, since the Jedi and Sith reduced each other down to a handful, and the possibility of suppression from either seems unlikely. An in-universe reason, preferably, I'm willing to accept anything from the extended universe or any other canon.
Edit: Many thanks to those who offered answers of other cultures that exist, but the question I'm trying to ask is more, why were there not more of them to begin with, and why didn't those other cultures rise up and take over the galaxy when the Jedi and Sith kind of left a vacuum? Why would people be forgetting the force exists (as the film seems to suggest) if there are other cultures still out there, and if they are gone, what happened to them?