Rebecca just doesn't care anymore; Before SU, she was confident in her abilities and knew what she was trying to create. Look at her posts online, where she said she'd fight for ideas on Adventure Time or her notes on characters designs for SU, with passive aggressive notes like "They have 5 fingers on each hand!!"
Now look at her - Her show was a runaway success, but the network didn't know what to do with it, so they just kept shoving it into corners and only showing off aspects of it, to give it the appearance of something they did understand. That fit their mold. They kept undermining Sugar trying to turn the show into what they wanted.
The fans also didn't help. No matter what she does, or what occurs behind the scenes of the show, it's all her fault. These 2 characters interacted in a way and a fan misreads the context so they complain about it online; say said fan is semi-popular online, having a few hundred followers. The message will spread, seeming worse, and Sugar while be bombarded with attack. This is especially harsher than a show like Adventure Time because SU is being used to bring attention to particular details of life Sugar believes should be addressed in a more understandable environment, so her trying to help is just deconstructed. Look at the hellfire she received for the Concrete incident, which she literally had no part of outside of allowing into the book.
I think Sugar is broken now. Her creation is no longer what she intended it to be and the network won't let it grow into what she wants either. Why force the effort of your crew into a better vision if it'll never be achieved? It's better to just stick to episodes about whacky Townies not knowing how to cook rather than explaining to kids that morality is grey, and that's alright, as long you know how to handle it.