"But I would never, ever, begin a new business that depends solely on Angular to survive. Why? Because Google doesn't need it. It didn't blink to give up GWT, it didn't have to think twice to decide to rewrite Angular 2 in an incompatible way to Angular 1, and so on."
This is just wrong - almost 3/4 of Google's web apps depend on Angular from what I have heard from multiple Googlers. If a rare instance where an Angular release failure occurs, it shuts down Google's development process dramatically & costs millions in productivity.
That rewrite is aimed at making Angular vastly improved - that doesn't equate to giving up on Angular, that is a poor analogy. In fact, Google decided to start investing vastly more resources into the Angular team, rapidly hiring and growing the team into a proper one, as opposed to it being a pet project of the Adwords team. In the next year or two, that ambition will bear much more fruit as mindshare grows with the realization of the technical problems solved & improved upon by ng2 - if React doesn't gear up to evolve, we'll probably see either a lot of defection to Angular, or a competitor that disagrees with the complexity that Angular introduces appearing to swallow React, just as React has done the same to grab disenchanted Backbone/Angular/etc. users.
Otherwise, the article does a good job explaining a lot of things, but it is very defeatist, as if it is futile to try to improve upon things. I can't say I agree with that sentiment, it goes against the heart of research/trailblazing/experimentation/etc.
It also makes some weak assertions, such as "One rarely benefits from big bang rewrites from scratch.", which is a generality being applied to every single situation, a fallacy. Confusing commonly accepted wisdom in development with an overextension of their meaning can lead to bad conclusions, as well as bad decision making.