What are we trying to solve by moving the world to UTC? We can't change when the sun rises and sets, nor can we change our circadian rhythms. So what we're left with is the fact that different parts of the world do things at different times. Using timezones, we set the start, midpoint, and end of the day to common numbers. If we ditch timezones and move to UTC-everywhere, we still have timezones. They're just implicit now. And we also have the new burden of our day changing while the sun is still up.

You waive off my dinner example as if "dinner" is a rigid set time. It's not. I'm in New York and I eat dinner at 6pm sometimes. Other times I eat at 8pm. Under UTC, this means that I sometimes have dinner on Wednesday at 23:00 and other times I wait until Thursday at 01:00. Asking someone over for "dinner on Wednesday" would always be ambiguous.

Here are some other confusing examples, if the dinner one doesn't illustrate it:

(At work)

    "What days do you have off this week?" 

    "I got Tuesday/Wednesday and Friday/Saturday off"

(At school)

    "When is the paper due?"

    "Tuesday"

    "The class that starts on Tuesday or the 
    one that ends on Tuesday?"

There's a reason we have the days change when most of us are asleep. It's a lot easier. A day encapsulates a day.

We could acclimate to all of this, sure. But we'd still have timezones. It wouldn't be immediately obvious to the Londoner that 11:00 is a terrible Skype time for her California colleagues (3am). So I don't see the gain here. Dealing with time differences is a fundamental aspect of living on a ball Earth.