I mean, you can do that today. Just post your hours and schedule your meetings in UTC.
Tineszones exist because we have two uses for time: the linear progression of the universe, and “where is the sun and what am I doing in the day”.
To communicate across wide stretches of the earth, you need a way to know where the sun is wherever the person you’re talking to is so you don’t call them in the middle of the night when they’re asleep.
We’ll always have something that lets us lookup "is the man in Madrid likely asleep if I’m eating lunch?”.
Tineszones work well for this because I can see that Madrid is gmt+1 and I’m gmt-5, so if I’m eating lunch they’re probably not in bed, because it’s 1800 there.
As long as humans care about where the sun is in the sky for how we order our days we’ll need timezones, even if we reinvent them and give them a new name.