Everything lands on the compositors. Features that existed for the past few decades in X and are deeply integrated into the ecosystem were relegated to second class citizens or just ignored

There were ten years that the desktop environment people wasted, where all those interfaces could have been created but they only started in earnest once the x.org devs put their foot down and said "nope we're serious x.org is unmaintainable we're not doing this any more".

And no, X didn't solve any of those problems -- what it did was provide completely unrestricted access to everything to anyone and it took multiple decades before different clients would stop fighting each other over control over the desktop. That clusterfuck was one of the things that x.org devs wanted to avoid, but they, not being DE devs, also didn't know what DE people actually needed. So they asked. And, as said, didn't get an answer.