I don't think that while ever ended! Have you seen Jetbrains' IDEs "new UI" (now the only UI except for a soon to be deprecated plugin)? You can't tell where a tab ends and the next one begins, it's just floating text on a solid background, with slightly more space between names. They also got rid of most labels, so it became a game of guessing what each symbol could possibly mean (another provably awful trend).

And the worst is, they're likely just copying competitors because as a sibling comment days, some people see the old accesible UI and think it looks old fashioned.