The thing that bothers me with not explaining Snoke is that it makes the whole Star Wars universe incredibly depressing. It means the saga never really ends. No matter how completely you kill the “last sith”, a completely new and ultimate villain can just pop out of the ether to kill and/or corrupt your heroes’…

There was a whole TV show with this trope as its central conceit. IIRC it was called Day Light and it subbed for Lost when it was on one of its breaks. Great show IMO, but was cancelled after the first season. Always thought that was a shame, they had an interesting thing going.