Even from this replay tell me that you don't think he's not under absolute pressure in full speed being tackled, with one man on the line, on his weaker food, after running 95 minutes in the game. Rashford has an open goal and many clinical striekers would have just slot it in. I don't think Rash did the wrong thing, the cut back was on, but Fred had awful lot to do. Funnily Rashford himself missed another bigger "sitter" right after for which he's not criticised not even remotely as much as Fred for his last ditch shot.
But this is life, sometimes palyer miss chances, you have to create enough of them to score which we didn't as a team.