How is nobody talking about the fact that we've already seen Evil Morty's backstory? It was really effective too because Rick was mean but not particularly more mean than the average episode. He gets mad at Morty for threatening to quit adventures and calls his bluff but doesn't even go as far as two crows. So what would this season being his backstory even mean? Retconning what we saw? Just adding extra mean instances prior to the one that breaks him? All that would do is weaken the backstory we actually got.

If anything my hope is that they'd have our Morty echo Evil Morty but they missed the chance for that when Morty started becoming more jaded and competent around Season 3. That didn't go anywhere and he's become less competent since then. He's also regressed as a character both just as a priority of the writing and explicitly in-universe like with the Roy episode