If there are other Force traditions in this future, like the Grey Paladins, I'd say that they could have become the go to form of Force training for Force Sensitives, and the Jedi and Sith orders are tiny because no one will join them.  They are considered outdated religions based on faulty beliefs about a fundamental force in nature.  It's essentially the way many religious beliefs are considered to be older, inferior, ways to explain things like mental illness (demons), medicine (magic potions), nature (creation myths, gods creating thunder/wind/weather/etc.) and the like.