I know on Earth we have a religious sect called the "Jedi", but this discussion is about the in-universe perspective...
Noun. The belief in and worship of a superhuman controlling power, especially a personal God or gods.
Synonyms: faith, belief, divinity, worship, creed, teaching, doctrine, theology; more a particular system of faith and worship.
Plural noun: religions "the world's great religions" "
Now, I think we can all agree religions are based on faith, faith in many things or faith in one. However the starwars.wikia.com/wiki/Force doesn't present any doubt to it's existence. It is 100% empirical.
That is to say, some ignorant gal on some outer rim desert planet may believe in it's existence without having confirmation, but it only takes a Force user to prove it for her.
Force wars have been a thing. The Force is part of the galaxy's history. So negating it's existence is easily refutable.
However, there are certain people (me included) that theorize that to use the Force you need conviction (or, well, "faith"). You need to believe in yourself and in the Force, you need to believe that you are able and that the Force will help you. This is the more mystical side of the Force.
Taking all of this into account I still hesitate when placing the Jedi, Sith, etc into the category "religious".
Those guys are, in my opinion, religious about the Force: They needn't have force-sensitivity yet they venerate the whole thing.