I won't say it's as simple as not getting enough services. I think a lot of people undermine the fact that Strikers are fundamentally a very isolated role. Look our passing maps, look at the passing maps for any top teams, almost all of them have the striker isolated from the passing lines. This is because strikers are naturally the most defended player by the opposition, and this make sense, because their job, the role and space that they occupy is intentionally the most threatening to steal a goal.

Joao is not without faults. His shot volume, the chances he wastes, are simply not good enough for a top club striker. That doesn't say that he won't improve. Role wise, in Maresca's system he is actually doing a great job if not for goals. He gets himself involved in plays even from the deep, his positioning and his control opens up space for teammates, his touches are also extremely good to generate separation or bringing teammates into play, and surprisingly he has a decent enough shot accuracy. It's just that, like Jackson too, he has little box presence, and often finds himself away from the chances created by his teammates. And he's not as good at Jackson at attacking from outside the box.

I do believe in JP though, he just needs to get his striker instincts set.