Steven Universe has a lot of problems, both from a quality standpoint and a problematic standpoint. The thing that gets to me the most as a black person is the show's terrible treatment of its black and POC characters. Both the episodes Bismuth and Coach Steven are just dripping with racist imagery and depictions, while other episodes like The Zoo (I believe that's what it called) makes light of horrific treatment dealt to black and POC people in the past. The show does plenty of other things as well, like trying to argue that the Diamonds- literal nazis- are sympathetic people who "made a few mistakes" when every single one of their actions in the show threw them far past the moral event horizon (especially awful in this day and age).  The show tries to teach abusers should be forgiven no matter what on the grounds that "they're family" or they just "made a few mistakes." The show also tried to create a trans metaphor with a cis character and genuinely doesn't see the problem with this. Along with that, characters like Stevonnie and the Steven-Greg fusion are uncomfortably sexualized despite them being fusions involving at least one child at all times, and other characters will hit on Stevonnie DESPITE knowing they're two kids in a trench coat. (This is something that stems from Rebecca Sugar's history of drawing porn of underaged characters.) There's a lot more I could cover, but those are the things that always jumped out at me the most.