He has much more innate talent than Fast/Lehkonen and the likes. The issue is fit and growth. He does not fit with either Panarin or Zib, so that's two wonky lines if he plays on them which leads to frustration. He has issues to go with his strengths. Skating, positioning in the o-zone/slot area (what are you telling him coaches?), style/fit etc.
Kakko's a possession player, he wants to keep the puck within the team and take care of it, he is looking for support that is not there - because he is playing with players who base their games on a different personal approach. Those players in turn get frustrated with him because he is not doing the things they need to support their flow.
When I said he played fantastic I was not being specific about his personal play, I was talking about the kid line playing "fantastic" relative to their age and situation, going up against seasoned cup winning vets deep in the playoffs. Then you took that word as a base for an argument about his personal play, supported it with wonky statistics (+/-) and it took off. The point was more that they have synergy as a line, the only line of three players to actually look like a line in my eyes. Yes, they are not playoff hardened vets, yet. But the more minutes the merrier as I see it. They complement each other nicely. Kakko gets the support he needs from Chytil and Laffy. Is it not interesting that they were the players who created actual scoring chances against the Canes away 5v5? The finishing comes with experience (hopefully) when they learn when to take their time and when to shoot directly etc.
This again leads to the first paragraph. How to create a situation where the kids flourish and grow. I know most people are looking to win, but I'm also looking at the greater picture. To me the growth of the kids is the real joy of following the team.