Nah they just had the remaining troops grab the left over equipment and start raising hell again. It's not a retcon. Though I can see where you're coming from in terms of devaluing the ending of the OT.
That was more something that happens between 7 and 8. In 7, the FO felt like sort of a blip on the radar that ended up having more bite than anyone expected. Then in 8 they were suddenly rulers of the galaxy with no explanation. I dunno, maybe they went around bluffing that they could blow up the system if they didn't submit or something. Kinda dumb but then again so was just about everything in 8.
He was resurrected. Happens all the time in fiction. It was dumb, but it was also an episode 9 thing instead of a trilogy thing.
The OT didn't have any loose ends to tie up. Of course it was going to be related in continuity only. I don't get why this is a problem.
Ep 9 dropped the ball in so many ways. Before then, we could chalk it up to the episode 7 subtitle, and I really kinda liked that.
But anyway, I don't see why this is a break of lore. If anything, it just implies he was naturally predisposed in addition to being trained. Big deal.
I can't tell if you're trying to defend the movies or have some weird issue with this one particular idea.
I agree with you that just about everything that happened in 7, 8, and 9 were dumb, though.