A lot of the problem has to do with the New Jersey Devils not making the playoffs for the past five years as that’s how huge rivalries build in the NHL. Even in the regular season the Rangers know they’re better than the Devils, they know they’re going to the playoffs, so the games don’t matter as much as they used to.
The Devils fight for their playoff lives every year now and thus while the games have potential to have meaning the Devils are out of the race by the time these two teams meet.
Not as Many Meetings
A big part of it is not playing the Rangers six times a year like they used to and instead have played them four times a season since realignment.