My biggest gripes with him are inconsistency and work rate.
A player who goes from 5 goals one season, to 30 goals after that and currently 8 goals this season. That’s some pretty wild fluctuations for a forward player at an elite club.
He’s our Theo Walcott in some ways. A pace merchant who started early and never really kicked on from what was anticipated. Split the gooner fanbase with people sticking by him no matter what and people thinking he had plateaued ability wise and slowly stagnated (the latter in hindsight were correct).
Go read this Walcott transfer thread from 2016 at Arsenal Mania. Some of the posts read eerily familar to this situation and Walcott was about the same age then as Rashford is now
https://arsenal-mania.com/forum/threads/theo-walcott-out.28986/