I didn't think Kuz was "awful" in this game overall, he was skating pretty well and it felt like the first line probably generated more quality chances for than against. I thought they showed some definite glimpses of putting it all together. Probably nobody knows if they can fully flip the switch like last year, but they're quite capable, I think.
I do agree that Kuz has put a target on his back by slacking in the regular season. If he bombs in the playoffs, it would make questions about his future a lot more relevant, and might put him on the hot seat as early as next season.
However, I'm very skeptical about the Caps' ability to benefit from trading Kuznetsov. Firstly, there would be no real point to trade Kuz for anything other than C. But then any C you're likely get back is gonna be either a lot less talented or will have as many or more question marks attached -- otherwise why the hell would another team do that?
Going for a serious talent downgrade to get a more consistent player would be a mistake, IMO. Most great winning teams have capital T talent at center.
The only real course of action, IMO, is to try to get another C with top-6 potential by trading other assets -- and then, IF that player develops into an elite C, and IF Kuz continues to underperform, then you can consider trading him.