The problem lies in that Cloud has already given up. He doesn't spend AC running around looking for a cure, he's not helping Tifa or any of the children. He's quietly locked himself away from everyone and moved into the symbol of his guilt and regret. He decides his death is "divine punishment" and spends his fleeting time brooding over his mistakes and ignoring all he has done. He's literally forced by others who confront him to take action and this is something that he wasn't like at the end of VII.

In AC, he's just given up, and the whole film is about him being pushed by everyone including his own psychological weakness of taking the blame for anything that goes wrong; and finally being put into a "happy place" where he feels better but he never once resolves his problems. Cloud never stops and thinks, "you know what? It really wasn't my fault. Aerith and Zack are probably laughing at me now for taking all the blame. I need to move on." He never confirms with anyone that he is finally over his guilt. I still imagine he'll be brooding over something else the next time we see him in a VII sequel. Its like he lives to be miserable and it really gets annoying.