From the experience I've had with something like world of warcraft, whos community is hard to ignore given that its an integral part of the game, I've learned just how loathsome fandoms for many genres can be, even ones that shouldn't form any kind of negative connotation to it.
I use to spend a fair bit of time on warcraft forums, and while occationally found some decent people to have discussions about game, lore, mechanics and stuff outside the game, overall it was never really fulfilling being part of a large community that clashed with each other on a daily basis. Though honestly I just took that on as it just being the nature of a gaming community that would be fighting each other ingame as well as on forums.
But, with the rise of the internet age and coming together of so many people, owing much to the greater internet fuckwad theory, it doesn't matter what your a fan of, just becoming part of a community of something you will find it anywhere. I currently love watched Steven Universe, and became a fan of Undertale, and do sometimes watch the current my little pony series all which I'd say are good cartoons and games that has a lot of value for young and old.
However, while there are a lot of awesome fans who do artwork, videos, reviews, animations, fan made games and merchandise for said products, just like tumblr, it brings with it the same dredges of society.
Now don't get me wrong, like anything, fandom has its good and bad, often you get some really creative and genuinely nice people who love the franchises, and often I'll look at their creative works and give them good write ups on what they've done. It just really drags down the appreciation for something as well crafted as steven universe, with its beloved characters and stories, when you have its fans telling other fans to go kill themselves. Its why I tend to avoid fandoms these days as much as possible, such as fandom associated sites.