My biggest issue with all this comes from the fact that Finn kicks ass the entire movie and Rey kinda doesn't. And then it switches at the end. So like Finn totally gets his fair share of badassery. Han Solo wasn't a Jedi but is genuinely more loved than Luke. I don't get why it can't be a similar situation.
Honestly? Because the context is different. You're right on one thing, we know for a fact that Jedi/Skywalker = Main Character in Star Wars, but that was fine in the case of Han because he was still a bad ass and got plenty of time to develop as someone that could lead his own stories.
And to be really blunt: Luke and Han are both white guys.
Unfortunately, this is a situation where two different demographics are very annoyed of playing second fiddle in big movies like this: white women and black people in general (but in this case black men).
One is thrown down as a love interest far too often, the other a satellite character or the sidekick (or the dead character, or the sacrificial lamb).
I like the idea of Rey having a much bigger and active role than Leia or, ugh, Padme. But I don't want to see Finn sidekicking. Like War Machine, Falcon, and many other examples.
There's also the other situation: they've been showing Finn with a lightsaber, not Rey. That type of swerve normally works I guess, but in this case? It's a bad idea. Because it's going to be a major letdown.
I don't know if you are black or not, but I am, and in the many circles I'm at, even the casual ones, seeing Finn with a lightsaber had a positive impact on people I hadn't seen before. They thought, "oh my god, a black person is going to be THE lead in a major sci-fi franchise." He will get to be the guy, the one that saves the galaxy.
This will kill that dream, and a lot of that positive impact will be fool's gold.
If the co-dependency thing works, cool. But this is a very thin tightrope JJ and co are walking. Especially in our current environment.