>>9676858Because it went mainstream, mass production with shorter less seasons with less plot.
CGI reduced the cost to make bad animation. But requires similar amounts of work to make good animation. In addition it forced the industry to have a skill shift where good 2D artists learned to character modeling and texture mapping.
Web and Light novels that are written by repetitive blog posts became to go to source for ideas. Because they fostered a base fanbase to leverage cheap new IPs. But transforming chapters of a story into a screenplay takes writing skills the original author likely lacks, but they likely get the author to modify it or just have the managers wing it. In addition the Web and Light novel format doesn't favor layered complex plots, it favors slow repetitive simple storylines.
Slice of life became a cash cow because Otakus use it to simulate friendship, love and life. Slice of life is the potato chip of anime. Cheap, mildly enjoyable, easily consumed, but utterly vapid.