I was morbidly curious enough that I watched the first season, and I don't get the whole Tumblr-inas and SJW sperging about this whole fucking show. It's just a decent kids' show filled with comedy, stupidity, action, and drama. The gems aren't really gays or lesbians because they're uni-sexual. Stevonnie isn't the first transgender character ever in television in a kids' show: Japan did it years ago with this character named Ranma that turns gender when he/she touches cold or hot water. The theme of one's identity, and tolerance and adversity in society in so much LGBT shows are rarely discovered in-depth because it being a kids' show kind of limits the message you are able to deliver because kids don't have enough social understanding for such messages.
There are shit tons of show out there that's about LGBT communities like Queer as Folk that are maybe even better than Steven Universe because they're more relevant and in-depth. This is like My Little Pony v2.0.