It doesn't matter now bro. Before it was Pionk, but Pionk isn't playing bad, in fact he is playing good. Stanley's advanced stats aren't even the worst. De Melo is so far down there and getting beat regularly now, but Stanley is the reason why the Jets are in this tailspin, even when he isn't in the lineup. Because the Jets are being outchanced with him on the ice. And as we all know xGoals matter. Because they predict how bad a player is likely to suck. What's the Jets PK with Stanley in the lineup? If the Jets win on special teams like they did early in the season, they win more than they lose.
There is a generally disdain for the Stuart/Chiarot/Stanley type of defenseman in this lineup. Always has been. And a genuine love for the PMD Niku/Chisholm/Heinola types as the way to win. I think Tampa, Vegas and Florida are recent examples of bigger defenses winning, with some good skaters to insulate them.
So I agree with Low Lefty, that it's a mindset the team has. So far Stanley hasn't replaced Dillon, and Dillon is doing just fine with a good team.
There's probably a lot of players Chevy would covet in free agency or in a trade as an upgrade, but the amount of good physical d-men available to Winnipeg on the market is likely marginally slim.