I think people are going a bit OTT regarding the demise of AJ and how he has no chance in the rematch vs Usyk. Usyk won the fight comfortably however you only have to look back to the Chisora fight to see how AJ will have a chance in the rematch and should have put up a better fight in the first fight. For a lot of the fight vs Chisora, Usyk looked very uncomfortable, struggling with Chisora's size and although he was probably doing enough to win the rounds, it wasn't easy. Even vs Bellew at cruiserweight, Usyk struggled in the early rounds when Bellew really went after him - iinm Bellew was up on the cards when the knockdown came.
To me it doesn't seem like AJ has recovered mentally from the first Ruiz fight. Pre-Ruiz, AJ would have jumped on Usyk and looked to take him out early, even if it meant leaving himself exposed but since the Ruiz defeat he's been a lot more cautious in his approach - against a lot of fighters he's good enough to win that way but vs Usyk (and Fury) he's going to struggle. If and it's a big if, he can overcome that mental scar then I could see him winning a rematch.