If you want to quit, go for it.
Skill progression differs from person to person, but there will always be a wall. Maybe you've hit that wall. Identify your technique; maybe it's bad. For example, I've never learned to wristjack until recently, which was stopping me from getting good scores. I learned it and the sudden skillboost is satisfying.
Maybe you're just overthinking it. I've always had this thought of not getting better ever since I started playing. That's just normal. You don't really get to see your improvement as if it was a school grade.
Regarding dans. I wouldn't think too much of it. Think of it more as a test. Maybe you're a runner, but you run just for fun, don't think much of your speed, stamina, whatever; but you improve naturally. Then, you test yourself. Maybe a 100m or something (I don't run lol) to test your speed.