Well, frankly, the main argument that Go used is that getting generics right from the outset was both hella important and hella hard, so they'd rather postpone it until they have a rather good idea of how the language is actually used in the wild and what the pain points of lacking generics are, and only then add them, in a way that fits Go's spirit.

Which would have been fine. In fact, if you read the notes from the very first implementation of APL you'll find that it was noted that they considered the lack of proper flow control as a gap that needed to be filled later.

Yet, even as the 90's rolled around you could find people writing articles in Quote Quad arguing that suggestions to add structured programming constructs to APL was somehow going against the spirit of the language.

Kinda sad it took 50 years for that attitude to change.