"I live in UTC+2 and you live int UTC-5, meeting at 15:00UTC?" ain't that easier? I add 2 hours, you take away 5 - math a 6 year old can do. And yet we refer to timezones with some made up meaningless words like Easter European Time - what does that even mean? It's not even accurate description as not all Eastern Europe follows it - pure madness.
Your phrasing was ambiguous. For a moment I thought you meant https://qntm.org/abolish. Still, you can't remove the past, and since the names carrying disambiguating meaning (notably DST changes, is UTC+01:00 CET or BST?) even if you remove them for the future the past still exists so you still have to handle them.
- I'm going to lunch I see you early tomorrow ? - But we have meeting this afternoon ! - Yes tomorrow, should I remind you we are UTC+12 ?
From the local perspective: "I always eat breakfast at 8am!" - two people can communicate when they eat (or do whatever). When you move to different country instead of sticking to your routine (minus jet-lag) you have to adjust your brain to completely different hours.
Benefits of using UTC internationally would only be good for companies and people that do a lot of international meetings so using UTC would make their life easier (instead of wrapping their heads around multiple timezones)
If you're not in UTC+01, it's easier to work out what time that would be for you than if I said I wanted to have a tele-meeting at 09:00 CET.
GMT does not observe leap seconds for instance.
UT1 essentially doesn't need leap seconds, because it is the correct mean solar time and not an 1Hz approximation of it (which UTC pretty much is).
GMT should be defined by UTC, but not the other way around