Claudius
I think the system is a bit of an excuse. I mean I do think he, Havertz and Jesus need to be linking up a lot more, but there's still a lot he could be doing better even in his limited scope.
If you watch Martinelli closely, you'll see he's still very immature with his movement. He's pretty potent with it already, but should be an absolutely nightmare for defenders. There's half a dozen examples each game where he should be sprinting for an overlap, making a run in behind, infield or to the goal like, but he'll end up ball watching or choosing the lazy option of dropping off into the easy space. He basically still plays a little like a 5 a side player and want's the ball to feet.
There's other small details too. He's also got a bad habit of going on the outside 9 times out of 10, ironically onto his weaker foot. Needs to come inside more often, especially when he's got the defender 1v1. Think about that Sevilla game where he had that fullback on toast. Every single time he beat him he went on the outside and usually down the line.
Both him and Saka are still young though. They're not killers yet.