Tell that to China, where there is one time zone for the country (when by geography there would probably be three or four for an east-west oriented country like it is). Yes, the official time is far closer to solar in Beijing than it is in Urumqi, but it is hardly unworkable.
China is the proof that it's unworkable! In Xinjiang, even though everyone is "officially" on BJT, lots of shops publish hours in local solar time and that's what a lot of people use for their actual lives. If an authoritarian government can't make people use time that's three hours out of sync with the sun, what hope is there to get liberal democracies to get people using time that's eight, nine, ten hours out of sync? It will just mean everyone uses informal local time standards, and now instead of making things simpler you've blown up the complexity by orders of magnitude.
It doesn't really work in China though. It seems to because so much of the population is along the coast and roughly aligned with the enforced time but you see people deviating from the official time in the West where the desync becomes obnoxious.
