There is a line where a show goes from being fun with a bit of drama for kids to being a drama with little fun for adults and you can see that when going through just the first few seasons of Adventure Time.
The show went from fighting a giant ice cream robot with weird business dudes in it to going and the main character's comical fear of the water to going to a village of depressed worms and dealing with toxic relationships.
Like you can do serious stuff in kids' cartoons, I remember Courage being able to handle this pretty decently with my favorite example being "Remembrance of Courage Past." Now even if it did slip up sometimes, like with the domestic abuse episode was retrospectively was a little too much but there was still fun in the show, Adventure Time lost its fun and that's the real problem with modern-day cartoons.