People's eyes glaze over when I rant about this. But yes, I fantasize about a world where you could say "let's set up a video call at 6" and there's no mental math when there's geographic distance involved.

Biggest downside I can think of, apart from the entire population groaning about making the switch, would be the confusion from reading literature from the before times. Oh, and all blood, sweat, and tears of all the devs who created timezone code going down the drain.