I disagree, all of those things are memorable. We just didn't have the instant gratification of social media and t-shirt printing on-demand (which basically exists to sell these kind of shirts within 24 hours, after that you've already missed the market) back then.
No question The Comeback against the Bruins means less with no Cup but it was still historic and no other Flyers team has done anything more than that one did (since the last Cup). 4th and 26 was still amazing and no other Eagles team before or since did any better than that one did (until last year). The best Flyers game I ever saw in person was in a first-round series against the Penguins by a team that did nothing (and kicked off a whole era of nothing).
I would say the only reason this one doesn't matter much is because the Eagles are the defending champion. It's not much of an achievement to win a round you didn't even have to play last year. But these last six or seven weeks have had their own kind of magic, and the unlikely underdog thing has been built into the team. As has unbelievable wins/luck.