One blogger explained they didn't understand as a child viewer, but after working in the arts and speaking to peers in the animation industry, they learned one of the main reasons was: unions. The European and Asian animation industries continued to put out innovative products while North American animation's lack of unionization stunted its growth.
I have been reading Japanese Anime/Manga magazines since the 90s, and learned that even in Japanese animation, how toxic the profession is to its animators, even when a studio does well in bestselling/award-winning titles. Even when a series grows an international fanbase.
More endless reasons for why the creative/performing arts continue to be defunded and/or underfunded...
Because Society LOVES its arts to consume, but won't LOVE its creators to enough to sustain them.