The PP was productive when Kessel was here. Kessel's zone entries and presence on the left side of the ice opened things up and gave our skilled players room to operate. That was always the case outside of a 4 game sample size in the 2019 playoffs. Now it's not.
It gave up shorthanded goals in his last season here, but now we simply don't score. The PP saps our momentum regularly.
Kessel was playing injured for a good part of this season on a putrid offensive team. It seems like where we disagree is that you're content to leave huge current net negatives on our roster while getting rid of potential future problems that were still productive and useful. I don't think that's the way a team whose best contention window is the next couple years should operate.
Being productive doesn't mean a great deal if you're just as leaky. The difference between 12th in +/- on the PP and the difference between 16th isn't one I see as particularly meaningful. Either both were problems, or both were okay. We've just traded different problems, instead of when in the playoffs, when it's the same - blunt on PP1.
And no, I'm not content with JJ being here. I'm just not going to fixate on that to the exclusion of all other problems. And given that Kessel was part of already existent problems, and given the personality clash was probably real, I don't see Kessel's role here as being potential problems. It was real problems there were probably going to get worse. And tbh, Kessel's issues with Arizona say they did get worse. No amount of linemates wholly explains a points drop of that magnitude.
The injury and linemate argument applies doubly to Kessel's performance this season.
Kahun performed well no matter who he was playing with, and only spent about 1/5 of his TOI in the top 6. Sheary without Crosby didn't fare near so well.
Sheary's most common Pens linemate other than Sid was Geno with 4:37, so I don't really see how you can judge ought there, and Kahun was in effectively top 6 attacking deployments for a bunch of time here. Their impacts here were pretty similar in pretty similar roles.
I think I'll leave both arguments there. My feelings on the broad important similarities are clear and I've no desire to get into an in-depth argument over just how much the many points of granular detail shade things.