Copying was always a problem in Japanese cultural products. Back in the '90s people were crying about Evangelion clones. And Evangelion was a tongue-in-cheek clone of previous mecha shows to begin with.
wasn't the late '00s simply the time when most anime enthusiasts finally got broadband and were able to stay up to date with the ever-current season? Blu-Ray wasn't adopted to the same extent as DVDs and people also got smartphones. Packaged media started dying, (legal) streaming began.
Also, consider that China took over Japan as the second biggest economy in 2008 and that K-Pop has exploded in the early '10s. Japan just stopped being competitive. Dubs in the USA stopped being made, cons started collapsing. Also
there was the depression and now there's another one.
I also like your point about the technological change on the production side. Don't forget about Korean and later Vietnamese outsourcing either... oh CGDCT means "cute girls doing cute things"... nonetheless there was the technological change of CG.
One could even add the effects of Abenomics, the entering in to the workforce of women and the re-entry of elderly people. The build-up of the military and the subtle but growing propaganda around it. All these economical and political trends revved up the amount of incels coming in the market. Anime was made by well-situated graduates of prestigious art and humanities schools now it's done by gig-economy hand-to-mouth subsistence incels for similar incels. It took a long time for the 20th century to end in Japan but it finally did and the middle class dies with it. Expect pre WWI West level of bachelorhood and the associated problems.
