It's probably not just one thing.
He's clearly lacking confidence in his play and has been since the start of 2024. He's always been diligent with playing defence and for the best part of a year now has been leaning on that side of his game and not attacking with speed and skill. Instead he's gliding around the middle of the ice playing safe.
His A-game is flashy, instinctive and carries risk but he's good enough that he can make those low percentage plays in traffic remarkably consistently without it being a problem. The Canucks do not play that way under Tocchet. Now team structure is the priority and Pettersson, like everyone else, is buying in to that. Early last season he showed he could adapt and put up points playing that way but it's never really looked like you're getting the best of him in the process. If the team wins it doesn't matter.
He's got a bad knee. Hockey will do that.
Futher context for those unfamiliar with the Canucks: the fan base is very dramatic.
When he didn't extend his contract at the outset of last season speculation that he doesn't want to be in Vancouver gathered a heap of momentum, even though we all knew he would still be an RFA at seasons end, and the cap works be going up so the wait-and-see approach made sense for a player who expected himself to build on a fantastic 22-23 season where he was the team's best player. A segment of the fanbase wanted to trade him because they thought he doesn't love them back, and then his game went to shit but he got his contract so everyone's piling on to the point Don Taylor in the OPs video thinks Pettersson isn't trying because he's not attempting to blow through Victor Hedman on his way to the net while PKing against Tampa's top unit. This time last year everyone loved the player and most Canucks fans knowing the rising cap would have signed him to the contract he got in an instant. Take the anger at his play with a pinch of salt.