It's personal preference at this point imo. There's no disputing Mahomes resume, nor the fact that he's been put in a better situation to succeed offensively.
I don't think McKenzie is a bum, but he's not a very good wideout. That's the main reason he doesn't need more targets.
I think they papered over the loss of Crowder until it became apparent the McKenzie/Shakir combo wasn't cutting it.
Dolphins have a different offense. They don't need to rely on churning out first downs because they have the kind of talent that can score from wherever.