Tarasenko used to be consistent offensively and inconsistent defensively, and now he's gravitated toward being inconsistent in both areas. He has moments where he dazzles us, whether it's a quick drive to the net or a gutsy backcheck to prevent an odd man rush. However, I am also seeing times where his idea of forechecking is to wave a stick in a defender's vicinity, or he's caught standing around in the defensive with no desire to retrieve the puck. I vividly remember an instance where the puck wrapped around the boards to Tarasenko's area, and instead of moving toward the puck he just stood where he was and forced Pietrangelo to have to push up to pressure the opposing player. Plays like that drive me nuts.
He absolutely has the ability to be a superstar in the league, but I feel as if he's missing that extra bit of drive. I wouldn't say he's peaked yet though. I agree with BlueDream that the turning point for Tarasenko has been that series against the Sharks where he couldn't muster anything offensively until the final game. Since then, he hasn't been as noticeable. But I wouldn't consider that his peak, I think he has a lot more to give and it'll take some time with his shoulder surgery being so recent. I do have doubts that he'll be able to elevate his game to that next level, but there's still a possibility, and so I can't say with good faith that he's officially peaked.