> Most people who rewrote their apps from X to Go and saw improved performance and readability benefited much more from the rewrite than they did from Go

Precisely, and isn't this presentation the perfect example of this phenomenon?

* Initially we had an implementation in language X

* We then rewrote it in language Y - the lessons learned by making the system anew (this time knowing the exact problematic spots, what really to optimize for, etc) - we got a better system. Long live language Y

* We then rewrote it in language X - the lessons learned [...] - we got a better system. Long live language X

Good programmers can productively write good and fast code in C, Python, Java, Go, or whatever. The skill of the developer and the understanding of the problem matters much more than the programming language