Rebecca was wonderful on the show of course, but people tend to hold her up as the patron saint of the show. She wasn’t exempt from bad writing *coughIncendiumcough*. While she was responsible for helping design characters like Flame Princess and Susan Strong, designing a character and fleshing them out are two very different things, and many of the other writers and storyboarders on the show did a great deal to give those characters depth.
Adventure Time wouldn’t be the wonderful show it is without the many other people that helped make it. Pendleton Ward, Adam Muto, Kent Osborne, Steve Wolfhard, Tom Herpich, Ako Castuera, Seo Kim, Andy Ristaino, Somvilay Xayaphone, Natasha Allegri, Jack Pendarvis, Cole Sanchez, Jesse Moynihan, Bert Youn, and countless others.
Rebecca was great, but the show has been doing fine without her. Enjoy Steven Universe AND Adventure Time and quit bitching about the past.