Time to reply to this.
Simply no!
The position of the inside forward is totally different from the position of the winger, and different skillset is needed
Salah and Mane, for instance, are WC wide/inside forwards but not WC at all wingers. They don't feel confortable playing on the touchline, and having to beat a man and then cross or pass to some one in the box to finish the move off.
On the contrary, they are happy to receive in or around the box and finish themselves the sequence after some flicks of their own.
Not an accident their proper position is in the half-space (left and right) leaving the flank for the fullbacks or for Henderson
That distinction is very crucial.
Some wingers can finish well, and some inside forwards can dribble decently, but that doesn't change the fact that it's not where they are the best and where they feel confortable
On all the names you mentioned:
Di Maria, Vinicius, young Neymar are/were wingers and not wide/inside forwards (current Neymar is more of an AM or number 10). Same is Sane and Coman for example.
Son is an inside forward. Same is Salah, Mane, Gnabry.
Young CR was a winger, from the time he started playing for RM he became an inside forward on the left. Maybe the only one I know who played both roles as well in his career.
Dembele is a winger, so is Raphinia. Ferran, Memphis and Ansu are wide/inside forwards. Abde is a winger.
See the difference? You can't simply efface it because some wingers finish better than others.
The off-the ball movement you ask is a skill that pertains not to wingers but inside forwards. You will never see Sane, Coman, young Neymar, Di Maria do that off the ball movement you ask, because they were wingers.
Now, I disagree about the root of his bad games at LW.
For instance, against Elche he was meh (given his best version always), but still played his position -> receiving the ball on the touchline, dribbling, passing, crossing, and generating chances.
On the contrary, when he starts as LW, he is never on the touchline, but in the HALFSPACe, the position where not a winger, but AN INSIDE FORWARD needs to be.
Because that's how Xavi's formation morphs with the different roles of RB and LB.
For instance, look at the formation in possession from the Elche game, and look where Memphis and Dembele are respectively:
Xavi has to do work here. He can't play with both Raphinia and Dembele in a 4-3-3 as one of them is wasted on the left. Until Ansu gets well to play the LW role, we need probably a different formation in possession.
PS: As for the tight spaces:
i) I don't think he is bad in tight spaces. IF you look how he beats his man, or 2-3 defenders that circulate him leaving no room, you can't say he is not good in those spaces
ii) It's irrelevant to the discussion. Reason is above and difference in positioning between an inside forward and a winger