> They spent almost 10 years saying "we don't need generics", but now are implementing it
You're making things up. Not a single member of the Go team ever said "we don't need generics". In fact, the FAQ stated from day one that they "continue to think about it", and that "Generics may well be added at some point".
Yes. IIRC, Rob Pike or someone else on the Go team even said something like "it's hard, so we are taking our time about it, may implement it later". Edit: see [1] below.
They've always also said "show us some compelling use cases", as if those still need to be shown ~15 years after after every other language except C got them.
Go's dependency management was designed after analyzing Cargo and its problems: https://research.swtch.com/vgo-mvs