Munir offers linkup to the team and has been a big part of many of the goals we've scored with Messi out of action. Even in our last game, his passing with Suarez is what led to us opening the scoring. That doesn't seem like nothing to me.
Just being 20 years old doesn't mean he should be expected to be some fast, tricky winger, so why is it sad that he's not? Even in the ranks of La Masia he was never that type of player. If that was what Lucho wanted he could have kept Adama, Deulofeu, Joan Roman, Tello, Alexis, or any other number of wing players who have left the club over the past two seasons that he's been in charge. Munir was a striker (A position he has not played for the first team since October of last year) who was able to get in good positions and put the ball in the back of the net. His best moments in front of goal usually involve him being in the middle receiving the ball, and it's clear that's where he's most comfortable. Why Lucho insists on sticking him (And even Sandro) on the right wing when Suarez is the only one of the three to have any experience playing on the wing is beyond me, but knocking Munir for not having the attributes of a winger when he isn't a winger doesn't seem right, and I suspect that has a lot to do with why Lucho isn't particularly worried about Munir and Sandro not living up to expectations, as they seem to really just be out there for match experience.
For what we could normally expect from a 20 year old who doesn't even have a single full season of Barca B play under his belt I'd say he's exceeded expectations during Messi's injury, which could not be said for Sandro.