McTominay and Rice both possess a similar amount of ability. The difference is the role in which each of them excels. With Rice, it's sitting in front of his CBs. With McTominay, it's pressing a little bit higher in midfield. Neither is a world class in his own right, but both are good enough to be members of world class teams.
If our plan for the future is to regularly field two attacking midfielders, the third midfielder probably needs to be a Rice-type rather than a McTominay-type. Which is unfortunate, because we already have two McTominay-types in the squad (if you include Fred). Filling that hole is an extra expense we could have done without.
I wouldn't be too upset if we bought Rice, but nor would I be bothered if somebody else bought him instead. In a limited role that's been tailor made for him, I think Rice has the potential to be great. But I'd personally prefer somebody who's capable of playing beyond a limited role when the game demands it.
So a better version of Rice would be my priority for the Summer (assuming Pogba stays). But if none is available, Rice wouldn't be too bad. Some of his qualities are definitely missing from the squad.