I really don't agree with this. He is invaluable because he both works hard and has the flair to try stuff near the opponent's box where if it comes off we get a goal. He will have loads more failures than successes but its better to try the things he does than the aimless crosses that many people want instead.
I'm a big Lamela fan. We are less effective when he doesn't play. Maybe tempering the amount of flicks and highly risky passes would help us to retain possession and face less counter-attacks but we're trying to attack at pace and generally, it looked very good on Sunday. One could criticize Dele and Son for regularly being offside or Son for shooting at the near post too often. They're true and need work but nothing too excessive. However, finishing is not his greatest talent. I wouldn't want to see him take another penalty. Left footed penalty takers have less success than right footed ones - it's a fact borne out by stats. He also hit it so that it was curving across Bravo (rather than around him if he'd gone left) at a very saveable height and distance. Eriksen takes them for Denmark. If Kane's not on the pitch, he should take them
If Lamela doesn't get back up to the level of last season, he will not hold a regular starting place. So the manager and he himself must be perfectly clear on this. And not just Lamela either.