Don't you think it's quite early to judge him as "mentally soft"? He has played 1 playoff series in the NHL and he was 20 years old in that playing as a 1c. The whole Panthers team didn't show up. "He has no killer instinct", what does that mean? He can't clucth the games by scoring goals in the final minutes? He wins games by shutting down the opponent's PPs much earlier and playing constantly great hockey throughout. Besides that, he has won plenty of games for the Panthers by his ice cold shootout finishes... that kinda goes against your claimed mental weakness he supposedly possesses.
I don’t mean just clutching games in the last minutes, although even that is part of being mentally tough and having a killer instinct. But what I mean still more is how the player can rise his compete level for the most important and biggest games in such way that he can substantially help his team and his line with his own personal play and effort. If you lose with your own game and with your own line and can’t really contribute with solid production in these most important and crucial games, then it usually has to do with lacking the mental strength that helps you raise your compete level that is usually needed in these really important big games. This is because the best teams always have these kind of mentally strong and still very skillful players, so if you are very skillful as Barkov, but seriously lack the mental strength, then you will get seriously exposed in these very important decisive games, as the other player’s compete level just simply exceeds your compete level. And as they have at least the same skill level, but the mental strength and killer instinct, you will get completely trashed in the biggest games, which is what has constantly happened to Barkov.
I don’t really have otherwise anything against the dude. He is damn skillful in so many ways. Although as I said, I don’t also see him as good in defensive play as some claim him to be. He is definitely good defensively, just not top Selke class in my opinion, because he gets still way too often scored against in 5 on 5 hockey. Not too badly, but still that often, that to me Selke talks are a clear overestimation of his general defensive play. His takeaways are for sure though pure magic. But for me the takeaways are still not even close to the most important part of good defence, because they still happen that rarely, and anyway they don’t by themselves lead into keeping the opponent enough off the scoresheet. And so far Barkov hasn’t been able to keep the opponents well enough off the scoresheet in 5 on 5 hockey.
But that I do admit though, guys, that he is still that young that many things might still change and develop in his play. But also it is good to remember that even despite being young, he is already becoming an NHL veteran when looking at the amount of seasons that he has played. So it might also be that his development is not anymore huge, as he has already gained a lot of experience, and gained probably the most of the skill development that can be achieved through pure experience gaining. Sure he might still develop in other aspects and in that aspect too, but to expect really huge development in that sense might be a bit unrealistic too.