I have favorites from many eras.Ghibli's Lupin, Gunbuster, Cowboy Bebop, FLCL, and The Tatami Galaxy, all come from different decades and are masterfully crafted. However, the best are outliers; none of those listed represent the contemporary industry-wide standard of quality. To define an era, one must look at its baseline.
The discussion of old vs. new anime itself is older than "old anime" if Rurouni Kenshin is anything to go by. As I see it, the main difference in each era is the culture. Audiences change, and different things are trendy at different times, especially with regards to character designs and plot elements. As derivative as modern anime can be, following the leader is nothing new. Even Trigun, one of my favorites, is unmistakably 90s. Good anime and bad anime are distinguished not by degree of conformity but by solid direction and intelligent writing. When I watch mediocre old anime, it appears the lack of these qualities can be traced back to incompetence, whereas the worst of modern anime often seem to be bad on purpose, as though it was cynically decided that the audience is guaranteed to show up regardless. That's the only major difference I can see: anime is more of a business than before. Still, it always was one, and my main point is that era doesn't matter if you avoid the fodder.

To me modern anime feels like it's a more competent and directed effort at trying to release endorphins in the viewer.
Since I don't appreciate this I prefer older titles that were worse at this, if that was even their goal.

I think funding is a double edge sword, lack of funding means shit graphics but the struggle involved might produce a decent product, While more money might produce something with outstanding visuals but mediocre story. (also having a pillow of money to rely on can make peoole lazy) Also there was a transition from hand drawn to digital, one is more labor intensive but pretty (at times) and the other has ways of making things much easier for the artist (although animators of the hand draw style do have various tricks they use.)
You don't exactly have to pay for dyes and ink pots for digital.
Also, i noticed modern animators using CGI in anime with mixed results.

There is something i cannot stand about modern anime and it's colours' saturation.
In modern anime colours are saturated to the point of insanity, everything is so bright like do i have to have my entire eyes melted?

For me it is mostly the art and animation style. Newer anime can have a great story, even as good as older anime, but the animation just doesn't look as good as it used to.
I understand the cost and time but I wouldn't be surprised if a lot of new anime would look heavily dated ten years from now with how the animate the shows today.

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By the way, older anime (in 80s for example) was literally drawed and sketched by people who wrote helluva amount of kanji in school, and its super visible on composition and outlines. Modern one is made by ppl who got little to no experience in kanji and it looks cartoonish.