I think the only problem is that he's played too much. Any player his age is inconsistent, and you need to take them out of the limelight at times. It's obviously a difficult balance here, as someone young with potential also needs games to develop, but we could've benched him more often.
Some may disagree that he even has potential, but I rate his first touch, that he's able to receive the ball when there's little space, that he can move the ball quickly, often in one touch, and his movement when we have the ball is very good. He makes the pitch bigger, and can run beyond his opponents. Still needs to hit the box more often when there's a chance, could've taken a few more shots when he's been in good positions, and he needs to work on every aspect when we don't have the ball. Doesn't get close enough to the opposition to be able to press, don't know where to position himself, can't really tackle at all.
But I don't get why he's started over 75% of our games. In his tucked in wide role, we have a very good option, someone who Henderson could've learned from and be rotated with. But for some reason, we never use Maxi on the right, we hardly use him at all, and I must say I find that strange. He might not be what he was, but he still moves the ball quickly, has excellent movement, even scores goals from time to time, and he positions himself well when we don't have the ball. When Meireles (who was used in the same sort of role under Kenny) was sold, I though we'd see Maxi a lot more.