C&P cause uni is killing me with writing just now...
I was alive back then but I don't have a definitive answer but I'll put out some theories.
Back in the 90s technology wasn't as advanced so making a track took more effort. Vinyl was massive and CD was starting to break through for djs. So tracks were around £7 and much more limited availability. Due to this artists were spending more time on tracks so potentially that's why the tracks sound better. I couldn't afford to buy every tune so it made sense to buy the tunes that were better for me.
Nowadays artists can finish a tune in days (right, Valency?). Using technology they can use a similar template for each tune and change keys and melodies. Is this great? No but I understand. Why would an artist spend months making a tune that will probably be leaked and downloaded of zippyshare before it's even released officially? There is no money in producing or running a label these days.
Was trance better in the 90s? Yes and no. Production quality wasn't as good but arguably sounded better. Trance didn't follow a pattern like it does now so originality suffers this way. I don't think drastic changes will happen soon but there does seem to be slight shifts happening. Tunes like Harvester or Mark Sherry's Evil ID remix don't sound like new trance (but a little like old trance) and seem to be doing well on Beatport. There definitely seems to be a market for innovation, see how popular Alex Di Stefano seems to be with trance artists. Maybe it'll take a techno artist to shake things up.
I'm kind of waffling now, so I guess the main point is if you want to see originality, start buying tunes. If artists start making more money they won't need to churn out as many "cookie-cutter" tunes (or they might and just rake it in). Trance doesn't sell now so that's why W&W etc shifted styles and now are constantly top of Beatport. People actually buy these tunes.
Or someone technologically advanced can figure out how to run an online label that pays the artists and labels better.
PS there was a lot of shite released in the 90s too.