His inclusion is a bit of a downer to me. I am also worried about how you can justify giving him minutes over the attackers that soldiered on throughout the Amorim era, and rallied together to qualify for the champions league under Carrick.
I also wonder what kind of message it sends that the club is reintegrating a player that downed tools and wanted away.
I don't really agree with the "soldiered on" point. Who exactly are we talking about? Rashford left because he'd fallen out of favour with Amorim and the relationship had clearly broken down. Meanwhile, most of the other attacking players from that period have either been sold or are on their way out - Garnacho, Antony, Hojlund, Sancho and potentially Zirkzee. So I'm not sure there's this group of attackers who battled through the Amorim era that Rashford would now somehow be disrespecting by getting minutes.
The reality is that hardly any of those players improved under Amorim and the football was awful. Amad is probably the one exception you could make a case for, and even he spent a lot of that period being used at wing-back. By the end, Amorim's attack was largely made up of the players he'd brought in himself.
I also don't really buy that Rashford simply "downed tools". He wanted to play football and, once it became obvious he wasn't going to get that under Amorim, he wanted to leave. That's not to say he handled everything correctly, because he clearly didn't. There were legitimate questions about his professionalism and, if Carrick does reintegrate him, that side of things absolutely has to change. From what I understand, though, he's largely conducted himself professionally throughout his career.
I also think the lack of leadership around him over the last few years gets overlooked. It shouldn't be used as an excuse because ultimately Rashford is responsible for his own behaviour, but where were the senior characters pulling him aside and keeping him grounded? This is a player who, when he was flying, was mixing it with some of the best attackers around. He's also one of the most scrutinised English footballers around, whether he's playing well or badly. With that profile comes an even greater responsibility to behave professionally.
Personally, I'd back Carrick to manage that situation properly. Rashford still has to earn his place like everybody else, but if Carrick believes he can contribute, I don't see why we should automatically shut the door on him because things went badly under the previous manager. The environment at United has been pretty toxic for a while and Rashford clearly hasn't looked happy for a long time. We're already starting to see a different atmosphere under Carrick, so if Rashford comes back into a better team, with clearer leadership and a manager who understands the club, I'd rather judge him on what he does from that point onwards.