Should and could golang have been so much better than it is? Would golang have been better if Pike and co. had considered use-cases outside of Google, or looked outward for inspiration even just a little? Unambiguously yes, and none of the changes would have needed it to sacrifice its priorities of language simplicity, compilation speed, etc.
It is absolutely okay to feel that go is a better language than some of its predecessors while at the same time being utterly frustrated at the the very low-hanging, comparatively obvious, missed opportunities for it to have been drastically better.
Joda time is an excellent library and indeed it was basically the basis for java's time API, and.. for pretty much any modern language's time API, but given the history - Java basically always had the best time library available at the time.
That “reign” continued forever if you count when java.time got introduced and no, Calendar was not much better in the mean time. Python already had datetime in 2002 or 2003 and VB6 was miles ahead back when Java had just util.Date.