I understand that, I even said I know why they did it but it doesn't change the fact that as far as movie villains go, this version of Ren (if he does become more evil or whatever in the future) isn't going to rank highly. I've seen some people call this the best Star Wars movie ever and if I had to say one thing to counter* that it would be that the villain isn't as good as Vader. Even if that's the point, that's still the case.
*there are obviously other things I could say to counter that
On a separate note, did they straight up blow up Coruscant? That's gonna fuck up some/a lot of expanded universe stuff.