"How is Rey interesting? Hes not really that interesting. The only reason he seems interesting is because we dont quite no anything about him. By the time his past is revealed, he will appear to be a much more boring character"

He plays the piano, he is loyal, he is crafty, and he has a past with Rau.
Also, we were all fooled into thinking he's a goodguy and now he seems to be a villain.
Who else does that apply to in Seed? Nobody. We all knew that Rau was on the bad side from day 1; unlike Rey.
In short, he has many sides to him.

If that's not interesting, then I wonder what you classify as such.

Note also that I don't think that "mysterious pasts" are very interesting at all.
Of course, I want to know what's up, but that's not how I measure what is interesting and what isn't.