It doesn't really work like that. Everyone has the responsibility to do their best in the context of the team. If one is more capable he does more, there's no passing responsibility at this level and there is no preferential treatment. Everyone has to do everything in their power to help the team. When Barcelona was in its prime shape and Messi was scoring/helping score more than Barcelona's defence could take on it was ok. When the team does not win and you did not give all, it's a problem isn't it?

Of course this is just a superficial comment and take it with some salt, I have no clue what goes on the pitch, it might also be that he cannot sustain a full 90min and be productive attacking while also doing a degree of defense.

Worth noting too that he can probably stretch the defense out just because he’s Messi. As a defender you’d be a fool to take your eyes off him.