True, and you’re right, this is to an extent subjective. I guess my point is: Islam represented a more intentional, less organic, form of synthesis. When the pre-Alexandrian mid-East cultures encountered Alexander and the Hellenists that followed, they weren’t ordered to make something new.
They made new things, yes. Isis was worshipped in Rome, and Hermes in Egypt.
But it wasn’t a directive per se, to make something wholely new. Mutual exchange among identities, but not an intentional directive to make a whole new identity. At best, the directive would have been to pay tribute to Rome… while remaining themselves.
The Christians did demand conversion, but again, their basic identity as Romans was seen as an inheritance, not something to scrap and build anew. And the medieval Christians would have seen themselves as continuous with this, with Islamic elements incorporated after the Crusades.
My only point with all this is that: original cultural creations in the classical world are basically threefold: ancient mid-east pagan, Hellenistic, and Islamic. There’s lots of synthesis and collaboration, but the original bases for future syntheses was Hellenic and Mid-Eastern, and Islam stands out as the one that *intentionally* made something new. It was still synthetic, but with a much stronger intentional basis than the syncretic Hellenists or the consummatory inheritors of that syncretic Roman culture, the Christians.
That’s all.