Why MUST a player have a standout quality at this age? What he's equally good at multiple things, nothing stands out, but no weakness stands out either. Messi at age 20 had nothing that stood out as his one strength, because he has multiple strengths. You could say his dribbling is his standout, but that's ignorant to his finishing, you could say his finishing stands out, but that's ignorant to his pace. You could easily argue it's better for players to not stand out at a young age and for them to be more all rounded, so they can be moulded into what you need/want them to be, rather than what their 'stand out' is. Would you rather have Walcott with standout pace, or a player that can pass, finish, cross and with some pace to burn? One player is one dimensional, the other has multiple aspects.
And I'm not saying it's bad for players to have stand out abilities, far from it. Just showing the flaw in your logic.
My point is that he's not rounded. He's a decent finisher, but he's not that quick, not a great crosser, not a great header of the ball. If he's got a strength it's his finishing, but even that is hot and cold as we saw with the chance he had yesterday to make it 2-1 in normal time (I think?). He's not good at everything which is the problem. When your game isn't rounded you need a stand out attribute and he doesn't have one of those either. That's why I was pointing out all the individual strengths of other players that were young.