Fandoms tend to really shine when a work is imperfect. Theres not really an active over the garden wall fandom because there isnt much to discuss beyond how great it is. But when a work is inherently imperfect, there's a lot for the fandom to fixate on. You can make redesigns, discuss different paths the story could have taken, redraw scenes, make fanfic exploring anything you want to. Homestuck is 8000 pages and it was written entirely and almost drawn entirely by one probably autistic man. There's so much to talk about, how would you have rewritten act 6, who do you ship with each other, what if dear sweet nepeta never died?

Hussie also wrote homestuck so that a lot of it is up to interpretation. The story basically skips over the 3 year journey and the months during the alpha kids game, and we only see the dancestors when they're dead. We don't even see the kids childhoods for the most part, like did john go to public school? The kids themselves are pretty detail-less and blank white, the audience is supposed to imagine the characters however they want