Look at him at Everton. He looked so nimble like peak Drogba. (He even did that Nani backflip in 2:52 min.). Now he looks like Drogba on steroid, huff and puff after every run.
Sorry, but the analysis from those commenting on the video is wrong.
Watch the video again, look at the goals he's scoring. A player is passing the ball for him to run on to, or crossing or cutting back for him to hit. Every time. He is running on to the ball, up to speed before the centre backs are near him.
Instead, at United, he is standing, and clearly instructed to stand, further up the pitch, in a central position, with a centre half already on him. Pogba is the only player in the midfield capable of playing those through passes, none other. Against Everton his supply line was Rashford and Martial from out wide, neither of whom can cross. For Belgium, and indeed United, he will continue to score the kinds of goals he's always scored - as a striker being freed into a pocket of space by another player's pass.
When that supply line is Pogba, currently 20 yards back in midfield again, for whatever reason, a series of players who have no pedigree in their passing whatever - Martial, Rashford, Lingard, Matic, McTominay, Fred - and full-backs who are raw and currently unable to get forward due to the lack of midfield control, you end up with one very unhappy centre forward.
Lukaku will score goals, if you provide him chances. He always felt like a strange choice for Man Utd, and I feel Mourinho incorrectly viewed him as a potential Drogba figure, when Lukaku's touch, body positioning, mobility and awareness were never in that league.