As a Go developer, I rarely ever miss generics. If you design up front with interfaces and the lack of generics in mind, you can almost always avoid needing them.
And for collections Go has other tools (like generator if you really want to). Overall in the 2ish years of writing Go, I only missed them when I was learning the language coming from years of Java.
Interfaces: same API, different source code. Generics: different APIs, same source code.
This is why Go needs to have generics.