The second season, Endless Eight really cratered a lot of goodwill (I myself have only bothered to watch the first season) and I think the light novels ended in 2011, so it could also be a case that once new content stopped coming out people simply stopped caring.
Meanwhile though people still remember Lucky Star fairly well, but Lucky Star didn't have a disastrous second season.
I wonder when the last time someone cosplayed as Haruhi at an American con was?
In the mid to the late 2000s there was kind of a wave of nostalgia for old school metal, spurred on in part by Guitar Hero, but you had the Tenacious D movie in 2006, Meatloaf came out with a new album in 2006, Iron Maiden had a pretty successful album in 2006, Dragonforce was pretty popular at the time and then you had the video game Brutal Legend in 2009, but since the 2010s it's basically been forgotten by the mainstream.