He doesn't build the whole argument on it. Generics just happens to be one of the most polarizing, most talked about subjects in the Go community. It's no surprise the author alludes to it. In his own words:
> PS: I like Go and have for a fair while now, and I'm basically okay with how the language has been evolving and how the Go core team has managed it. I certainly think it's a good idea to take things like generics slowly. But at the same time, how things developed around Go modules has left a bad taste in my mouth and I now can't imagine becoming a Go contributor myself, even for small trivial changes (to put it one way, I have no interest in knowing that I'm always going to be a second class citizen). I'll file bug reports, but that's it. The whole situation leaves me with ambiguous feelings, so I usually ignore it completely.
The author's primary complaint is the way Go modules were handled, namely that one member of the Go core team overrode the entire community.