He hasn't scored, but I haven't noticed any lack of effort. There have been quite a few games where he's been among our busiest players, and were it not for some woeful finishing he should have more assists.
He sometimes dribbles into walls, and doesn't make the best decisions. But he's always had that problem.
Basically, I think this is yet another load of BS. Mane has gone from "We shouldn't even sell him for 50m" to "meh, I doubt anyone even wants him" this season. No one was complaining about Mane 2 or 3 games ago.
We lose, someone has an off-game and that player immediately cost us the match and has a bad attitude to boot. It doesn't even make any sense. But rather than when the facts don't fit the theory, people just decide that it can't be them that's wrong... it's that Mane isn't smart enough to figure out what to do.
The guy apparently has trouble showing up on time. That's a problem. But to me he still looks like he's working pretty hard (if not always effectively) on the pitch. And that the supposed attitude problems and complaining on this forum are not related to anything he does, but rather how the team performs.