That requires vastly more work to produce any results at all, to the point that most animation people might want to produce never gets made because the process is far too expensive. Mediocre animation that gets made using AI tools is better then high-quality animation that never gets made at all.

Blender and AI tools both have their place but they’re not interchangeable. And just wait until Blender starts incorporating AI, which it will, because the purpose of something like Blender is to use computers to automate most of the work that would need to be done with previous generations of tools, and AI is just an extension of that. Animation will exist on a continuum from fully handmade artwork to fully machine generated artwork. Unless you think everything should be drawn by hand one frame at a time, you should be happy about everyone being able to produce animation in a way that suits their skill level and the amount of time they have available.