I don’t really think TFA screwed over TLJ & TRoS that hard. Redoing the Rebels v Empire conflict was a mistake, but they could have brought in the Republic military as late as in Episode 9, and there’s more interesting subtext to the conflict you can read into TFA and TLJ.

They don’t develop on the new concepts of the ST that much, but TLJ picks up the slack enough that I don’t think it’s a problem. At least in TFA’s case.

The Knights of Ren should’ve been cut, because there’s not really anything you could do with them. That’s kind of indefensible, but it’s not that big a deal either.

I don’t really know what else could be a case of TFA screwing over the rest of the ST, though.