I think the main fear people have isn't the concept of generics, but the implementation of generics. Go's primary goal is simplicity, and implementing generics isn't simple.
This seems to be slowly changing, but Go was designed to be a solution to Google problems - python being slow but some c++ applications taking literal hours to compile. Keeping that perspective in mind makes it easier to understand why Go maintainers have not accepted an implementation of generics into the language yet.