Probably is, honestly
Way I see it though is that Sterling was constantly getting gametime in his favoured position with attacking teams that suited his style, thus helping his development. Is Rashford getting that? If he were, I'd back him, but right now? I just think that being played the way he's being played, in a team that's pragmatic instead of pro-active... It's not the best way to nurture an up & coming attacking talent.
Which is why I feel he'll fail at the very top level, or maybe he'll just peak later than most.
Jose isn't SAF, he won't be around here forever. He won't even last this season. Apart from that, there is a tendency to get carried away with recent form and write off everything they did in the past.
For example last season,
In CL
Came on as a sub and scored 3rd goal vs CSKA away
Scored our only goal in 1-0 win against Benfica away (GK error)
Assisted second goal vs Benfica at home in 2-0 win
Scored winner against CSKA at home in 2-1 win
Assited our only goal vs Sevilla from Corner
In league
Assisted first goal vs West Ham in 4-0 win
Scored first goal vs Leicester in 2-0 win
Scored equaliser vs Stoke to make it 1-1. (it was comical goal though)
Assisted first and third goal vs Palace in 4-0 win
Scored our only goal vs Huddersfield in 2-1 loss
Assisted third goal to make it 3-1 vs Newcastle
Scored equaliser vs City to make it 1-1
Assisted first goal vs West Brom in 2-1 win
Scored 2 goals vs Liverpool in 2-1 win
Scored only goal against Watford in a 1-0 win
Apart from Liverpool, Watford, Sevilla everything happened in the first half of the season when Martial and Rashford played alternate games as left wingers. Then we signed Sanchez and both Rashford's and Martial's form went very bad.
Just see how many times he either scored or assisted first goal in half a season, that's very good for a 20 year old playing as winger.
Obviously he should improve even further as Manutd will keep on signing players but few of our fans just can' wait to write him off.