Rivalries ebb and flow, peak and valley over time. Sometimes one team falls off for a long enough period that the general dislike is still there, but there's just something less vitriolic about each meeting.
In the the late 90s and early 2000s, it was the Devils as the Flyers' chief antagonist. Since the '04-'05 lockout, it's been the Penguins. And, really, after Eric Lindros flattened Mark Messier and company in '97 Eastern Finals, the Flyers' rivalry with the Rangers had trended more towards one of those valleys. Don't get me wrong, no one started liking the Rangers all of a sudden, but the passion for the rivalry had waned for some, if not many.
That said, it doesn't take much for one of these long-standing feuds to get reignited. In fact, getting waxed 0-6 in a regular season and losing a Winter Classic at home just might do the trick. It seems to have for coach Peter Laviolette.
Lavy, like you, can't believe the Flyers were unable to take even one game off the Rangers this season. In part one of his offseason mailbag, he answers a fan question "the biggest surprise on the season" for him:
It's worth noting that outside of two to three occasions in which the Flyers clearly couldn't hang, including those back-to-back weekend afternooners on Feb. 5 and Feb. 11, they skated with the Rangers and could have, perhaps should have, split that season series if a few extra bounces gone their way. Without dispute, they could have at least taken a game (see: Winter Classic).
The histrionics of this year's first round series against the Penguins aside, if you can manage to put them aside, doesn't it feel good to really passionately dislike the Rangers? If only it didn't have to take a season sweep to get the fire burning once again.
Unrelated Note: The Flyers' stylize Lavy's nickname as "Lavi." Your thoughts.