>>281509510
I think it's less about deep themes and more about ambitiousness of the works. I'm not going to say everything was ambitious in the good old days or whatever, but the constant LN and even WN adaptation barrel scraping pollutes the ambitiousness of modern works since the underlying framework can't really be fixed.
These stories are often very grand in scope with hundreds (sometimes thousands) of chapters, but thematically they say very little. Something that really stuck out to me was when I watched Cautious Hero; I could see the underlying efforts of the studio staff, from the fun visual gags in the animation to the framing of events, but it's like the whole team was shackled by the writing in the original work.
Parasyte is on the other hand a fantastic adaptation of the source material, both the manga and anime stand in their own right. Because the studio had an excellent skeleton to draw from they were capable of creating their own slightly different take on it that was (in my opinion) equally as good.
This doesn't touch on the fact that proportionally less original anime is made now too which exuberates the issue. All in all it's primarily a symptom of the harder economic times in Japan, where now the main groups who field money for anime are publishers that are in need of an advertisement for their media that actually makes money, so consequently even more anime than before is an advertisement for other media (which of course was a thing in the past as well, just proportionally less so).
