If generics replace code generation or hand coding a concrete implementation for specific types or... operating against interface{} and then switching based on runtime type, then I strongly disagree that it makes reading Go code harder, it makes it, IMO, easier.

But that's the thing, it's just IMO.

Code is written to be read, and typically for other people to read. So, in practice, it is only optional if everyone else agrees to not use it.