"Not because of the missing functionality, but because you can't talk about go without somebody bringing up [the GIL]."

It's better these days, but for a while it was a common point of contention.

it was slightly different: Anybody who wanted to try implementing a gil-less python could. The reasons of the status-quo were well explained.

We only get hand-waving from the Go core devs.

Adding generics to the language affects the language and reimplementing an interpreter/compiler for a language that fixes a performance issue without being incompatible are two completely different things.