The problem is that we don't know exactly if Rashford will ever truly develop or if he's even a good player. He gets himself into good positions for his age, and he's definitely up to the challenge physically. His big flaws are his finishing and overall football IQ, both are normal signs of a young player, but the lack of progress over the last couple of years is potentially worrying but he is still young right now so it's just a potential negative.
Obviously, Sterling takes it for me without a question, but the fact that these threads get posted (along with Rashford vs Mbappe) shows that there is a segment of the Caf that really overrates Rashford or even the possibility of him reaching his potential. I think people need to cool off on the kid, because right now it's really 50/50 if he will truly come good on his perceived potential.