a) generic programming is a new thing
b) any of those people you mention aren't using go for some things and other things where this feature is desired
c) that the feature will 'at best' be at level X
d) that level X won't be enough to satisfy some use cases
and a whole host of other things, not least of which the fact that go itself was invented to suit some purpose after other languages existed, and has been successful for many users
Any new language is already playing catch-up to reach the state of the art. Go is 10 years old and in those 10 years has made astonishingly little progress at implementing basic features such as error handling, because the designers cannot escape their bubble.
The most sensible thing to do is to kill Go, not to improve it. The root problem is not the lack of this or that feature, but the bizarre beliefs of the people running the project.
Care to expand this? It's pretty clear that you don't find Go suitable for your own use cases, but I've found it to be an extremely productive language, despite the fact that it may have a couple of warts.