Niskanen is good because despite his pretty heavy defensive deployment against good competition his relative shots against, expected goals against, and actual goals against per 60 are amongst the best in the NHL since he’s been in the league.
And he was their most heavily used 5v5 defenseman last postseason where when it mattered most the Capitals were able to tighten up defensively.
It’s fair to think that maybe Niskanen’s best days could be behind him due to his age. But the vendetta you have against him, with no actual evidence to support any claims you have against him, is complete garbage. Everyone knows I have offered up unpopular opinions in the past but I’d at least try to support those claims with some form of evidence (often times unsuccessfully). With you and Niskanen it’s just “he’s not good because I say so.”