There’s nothing wrong with just enjoying what’s on screen and not engaging with it further. But if I love something, I want to continue to engage with it past what’s on my screen on Sundays. And we’re discussing the hypothetical end of canon. If the show got a cancellation announcement tomorrow, there would be no more new canon. So what does the fandom do after that? Do we continue reblogging the same finite amount of gifs or do we create more for these characters whether that’s through art or fic or meta or whatever. I just feel like for a fandom to exist after a show or book or movie series ends, you have to keep creating.
Stargate SG1 has been cancelled for a decade but there’s still several very dedicated gifmakers for it on tumblr, that bring out new sets frequently. I’m only on the edges of that fandom so I don’t know much, but I do know they have weekly rewatches of the show and awards every year for fanart/fanfic.
So yeah I think fandom can keep creating, and keep existing. I hope that happens for Rumbelle, I don’t see why it can’t if enough of us want it.