Proper abstraction can have a huge upside by allowing people to understand a part of the project without the need to understand all of it. We're using abstractions all the time really, you don't need generics for that. An iterator, a collection, a file, a network connection, a database table are all abstractions. You don't have to read N millions of lines of database code to learn how to use a database. Abstractions like these are good.

Abstractions where the description of the usage (API) is just as complex as the implementation are bad, and I bet you can create them in Go quite easily without generics. At least I know it is possible in Java, and also was before Java 5.