dialects with regional substrate and vulgar varieties; koine written greek is a rather late standard, perhaps not byzantine, but koine literally means "written", in contrast to spoken.
> lifestyle
like what? Sedentary, sure.
> music
music-ians, who were not the same everywhere
> alphabet
again, regional variants exist, writing style wasn't fixed
> commerce
commerce is competition, so how could it be unified? associated towards outsiders, perhaps.
> military style
I wouldn't know about that, but Sparta vs Athens thousand years earlier would be a common counterexample
It's debatable how hellenized the Greeks on the anatolian cost were, the Lydiand, moesians and cetera. "barbaros" relates to speech first and foremost, though I am not buying the etymology. Speakers of other mother languages would have reasonable trouble getting the pronounciation right, so a Scythian, Tracian, Dalmation or otherwise "Celtic" Slave would appear hard to comprehend.
If you are generalizing a millenium of history, you are all history barbarians.