So interesting perspective on Rashford and perhaps some middle-ground to be found in the debate on both sides...
If you check out Rashford's statistics on FBREF and see his percentile ranks against players in the big five leagues over the last season, its interesting to note that you can select two views, one 'vs forwards' and one 'vs wingers'.
When compared with wingers, Rashford scores in the 90th percentile for goals per minute but poorly for basically everything else you'd want from a good/elite wingers i.e. successful take-ons, ball carries, progressive passes, assists etc...
When compared with forwards, Rashford has a very mediocre goal return and is only slightly above average for assists - but his take-on's, ball carries etc...are now high by comparison to CFs.
Could it simply be the case that Rashford is a player that can be very good when used in one very specific role, almost as a forward playing from the left, distinguished from an inverted winger/wide forward in the sense that he is often the furthest player forward and acting as the main attacker.
But...when playing as more of an AMLF, with a CF, which means tracking-back and being involved in the build-up, he looks very, very limited?
Haven't delved massively into this, only looked at the last 365 days. That's probably a fair snapshot because its contains a hot streak and a cold streak so likely averages somewhere around his mean.
https://fbref.com/en/players/a1d5bd30/Marcus-Rashford
Could be summarised as a poor winger but a good goalscorer from the left or a limited goalscorer but more mobile forward through the middle