Earlier quoted context omitted.
I like that the mantra went from "move fast and break things" to (paraphrased) "move fast and don't break things".
It's been a pretty poor mantra from the beginning anyway. How about we move at a realistic pace and deliver good features, without burning out, and without leaving a trail of half-baked code behind us?
I think it's probably less fun to gradually replace things with better things than to - say - write your own alternative PHP backend.