I agree that a mess looked (sadly) inevitable based upon that post and some of the other surrounding context. E.g. Guido citing Yoda conditions, how dumb that game can be, and getting ignored.
But just because the feature shipped and design-by-committee is upon us doesn't mean we need to accept the outcome. Why couldn't there have been a more evolutionary path for this feature? For example, there is surely a way to write a prototype library to accomplish the same effect with slightly different syntax. (How about a single function `walrus(a, b)` that does what `:=` does?). Then let real user adoption drive the change. Maybe somebody will discover case statements from scala and want that instead.
I hope the committee models some amount of their work after WG21. C++ hasn't evolved so effectively because some people were magic visionaries. For the past decade, C++ has mostly ridden on the proven success of boost. And skipped a lot of the parts of boost that suck.