I’ve been working with Go for 10 years and I have no idea what you mean by maps being generic before generics came along, nor did maps ever cause me to have over-verbose code bases. The links didn’t seem to help.
Trying to summarise what they were likely saying: Not having generics makes code verbose because you end up copying and pasting your library code to make it handle different types. The complaint about maps being generic was that the Go team clearly saw a need for generics (as they implemented them for maps and some other types) but decided that others wouldn't need them. So they had one rule for them and another rule for everyone else, which people don't like.
So when something is generic, it means it is a type parameterized by other types. So the type map[string]int is indeed generic, but no language users could create their own type btree[X]Y, for example.
Essentially, the go developers saw a need for generics and then decided that only they get to create them, where most modern language developers either make them available for everyone to implement or don't add them at all.