Computer programs are tools. It doesnt do anyone any good if they're unusable in the name of chasing moronic trends.
Old interfaces were far more practical for getting work done, and therefore obviously boring.
For me, as someone who is supposed to use technology as a tool and not as a source of amusement, the new interfaces of the major OSes feel unacceptable. But the other billion people chatting and scrolling are the real consumers, not me — and as a result, we now have the interfaces we have.
Software makers treat UIs the way auto makers treat paint and body styling.
All that said, I truly miss the days when we had interface skinning. There was a skin for OS X called UNO that was absolute perfection in my eyes, and it was ported to an old version of Android back when skinning was a thing. There's nothing like it available now. Even GNOME is highly against theming and skinning now, apparently because they like breaking with every single release rather than maintaining an API/ABI and skinning support. The themes that were available for Windows XP were so much fun, even if you had to swap out DLLs to get them working.
Focus-group based and UX research was a lot more intense in the 1990s compared to today, and late 1990s UIs are still among the best available.
Material is what made me hate google. It makes everything so difficult. It doesnt even look good. It's a low contrast sea of modern bullshit.
I sincerely hope that the material designers go to hell when they die and are forced to use their own garbage designs for all eternity while those of us who dont suck can use properly designed software.