While the GP was a bit...harsh, the main reason people have that view is generics, as a problem space, were solved. Java's way was published years ago. As was .NET's. Other languages exist which have some form generics. The argument of "gather enough use cases to decide on the matter" feels like a punt given the use cases already exist and were known in the industry for the past 30 years.
The problem space may seem solved, but apparently it's still not as easy as it looks from the outside. You don't have to take my word for it, Cthulhu_ linked a comment by Russ Cox (a major contributor to Go) from a few years ago above: https://news.ycombinator.com/item?id=9622417
> We have spoken to a few true experts in Java generics and each of them has said roughly the same thing: be very careful, it's not as easy as it looks, and you're stuck with all the mistakes you make.
Perhaps. But in hindsight, Go's generics implementation turned different enough to warrant benefit of the doubt in my opinion. A notable difference is that Go interfaces are implicit while C# and Java are explicit and that affects Go generics.
