I talked with a few people who wrote Go servers and while they loved almost everything about the language and ecosystem, they hates the missing generics so much, they still switched to other languages later.
Writing code-generators for everything wasn't fun.
I don't miss generics in Go and I have used generics in C++ a good deal. I think the whole generics argument against Go is largely parroted by people who may not even know what generics even are. C doesn't have Generics either. It's doing OK.
Any language that doesn't have generics, including C and Go, have to work around that limitation. In C, people get around this by using void* (equivalent to using interface{} in Go) or code generation via macros.
I'd flip what you said and say that most of the people arguing against generics in Go don't have much or any experience with them. Which makes sense because a large number of users came from dynamically typed languages.
Writing code-generators for everything wasn't fun.