I don't necessarily think he's wrong, though I wouldn't say for sure that Kakko won't be better than all of them in the long run. I think there's a tendency to overvalue players who are doing really well in lower leagues and undervalue players who aren't lighting it up in the NHL. Also, there's a strong bias toward point production. People are always going to be more impressed by a guy putting up 18 points in 7 WJC games than a guy putting up 17 points in 48 NHL games, no matter the context or how well he did in other areas of the game besides scoring.
The amount of improvement Kakko showed from year 1 to year 2 was astounding, but it was mostly in his play without the puck, so it goes unnoticed or unappreciated by most people. I think this year, with more ice time and better opportunities, his offensive game will flourish.