Those shows have always existed, Barney, Teletubbies etc. Difference is most cartoons are now either
A)Lowering themselves to the Teletubbies-level of inoffensiveness and just bright colors mixed with loud noises.
B) Or alternatively they aim for the preteen to teen audience but not in the cool Avatar way of "epic fantasy adventure with likeable characters and some adult themes slightly in the mix-way. But more in the "Shallow pointless adventure thats an excuse for the PC virtue signaling"-kind of way.
Its funny too how every children's to preteens show tries to be Adventure Time. Early Adventure Time was more of a traditional adventure disguised under the Barney colors and loud noises. Eventually even Adventure Time itself wouldn't be spared and turned into category B) show and became shit. Meanwhile all adult cartoons try to be more like Rick and Morty but then just swear and make a lot of poop jokes and ironically turn more juvenile than the inoffensive Teletubby-NotAdventure Time-shows. The new generation of writers draw their inspiration from their retarded Deviantart-fanfics instead of old adventure books, while producers demand increasingly inoffensive shows, resulting in all modern shows eventually being made for children, or rainbow-haired manchildren.