I don’t find that argument at all compelling. I didn’t reread it all again now so am replying somewhat from memory, so won’t address all the points, just the main ones I remember: that it boils down to “but then I won’t know if it’s the middle of the high/the business is open in other country!”, except this is already true:

Countries have weird time zones like how China has a single time zone even though the country spans the area of three. Apparently Palestine and Israel have different time zones despite being the same physical location. It gets dark at different times depending on how close to the equator you are. If you want to know if it’s night or day somewhere, you already have to look it up, so nothing would change if time zones were abolished.

Similarly, businesses already have varied opening hours so again you have to look it up. Hell, without time zones it would be easier because if the website says “you can call us between 0900 and 1700“ you know that you can call them when your clock is between those times, no need to mentally time zone adjust.

My point is that the arguments against laid out in that post, by and large, are already the case so things don’t really get any harder, certainly not after we adjust to the idea, but without time zones we have a single consistent time, we just adjust our schedules based on our local day/night. Hell, if more people work from home and more companies hire foreign remote workers, a shift from local to global time would benefit everyone.

You forgot to cover the part where day names lose meaning -- you go to work at 21:00 on Wednesday and come home at 06:00 Thursday. Basic concepts like "tomorrow" start to come apart at the seams. (Yes, shift workers already deal with this; no, that doesn't make it easy.)

Meh. These are more like objections to the first few weeks of adjustment, than to the new steady-state.

People are quite adaptable. Look at the giant changes in working hours, open hours, & distance communications from the Covid-19 epidemic. People got a crash course in the variety of other times/workplaces/rhythms that others considered necessary or possible... and managed.

The decision-supporting knowledge "it's 4am there" could simply become "it's 2 hours before sunrise there" - and trigger a confirmatory "are you sure?" dialog, or offer to remind of the ideal time-to-all, from the communications device you're using.

(In fact, there's a giant range of potential new ways to signal ambient awareness of not just a destination region's openness to calls/messaging-interruptions, but every individual person's openness – and global UTC might be just the impetus to drive innovation in the phoning/texting apps.)

you can come up with a huge list of bad reasons for anything if you assume the thing you like/currently have has a good and easy answer already like in this article.