My opinion is it’s mainly the “appeal to past” or “appeal to tradition” fallacy which makes people say what is older is better. The new music coming out to me is just as good as it was. I think because it’s produced with modern equipment it lacks the nostalgia factor of a grungier production sound maybe. It’s like the people who yearn for vinyl and don’t like cd’s.
To me the only thing missing is maybe more of the Gangguru - Be Your Own Guru, Kuru & Charm - Japanese Vibrations, Battle of the Future Buddhas style where it’s lower tempo and more subdued.
Some uptempo style songs can sound generic and machine-like, but, like anything, those are just the songs that didn’t work out as well. 95% of it is just as good as predecessors. I don’t know how anyone can listen to E-Mantra, Proxeeus, Morphic Resonance, Filteria, Jaraluca, etc etc and not say it’s just as good as the 90s music.
Then there is Ufomatka, Goa Luni, Katedra, The Maniac, Tranquillity Base Project who are doing somewhat different thing.
In my opinion the music is just as good, and there’s a tendency to jump to the judgement that because the 90s music is older, it has to better.