I don't think this is right. I think many on the left would dispute any differences of any kind between ethnicities or races. Hell these are the people who refuse to acknowledge any difference between men and women.

Hence 'serious people', people actually familiar with the research in question and not in a position to deny it. Folks like Eric Turkheimer or James Flynn.

The Egyptians invented writing, so did some Semitic peoples (Arabians and Phoenicians, deriving from Egyptian), the Sumerians invented writing, Greeks Linear A, etc.,

The irony is that the Minoans were not Greek. Were they even Indo-European? Certainly open to question. If they're more closely related to Phoenicians, it would mean that no European people invented an alphabet. But that's OK.

Later, Viking runes seem to be an original invention

AFAIK, it comes from Latin.

Likewise the alphabet evolution from Greek -> Etruscan -> Latin involves some very large shifts and evolutions.

The Greek being obviously the most revolutionary. But we were talking about the actual invention of writing. Considering that it was not invented that often, I'm not ready to blame Melanisians or the inhabitants of the Canary Islands for not doing so.

Phoenician -> Greek is a much bigger shift.

Probably the biggest one of all. But it is not invention.