I outline in a ~20 page whitepaper why Mithril for JavaScript/TypeScript UIs (plus Tachyons for Atomic CSS) is a better choice over React and Angular for Single-Page Applications based on experience with all three: https://github.com/pdfernhout/choose-mithril
"tl;dr: Choose Mithril whenever you can for JavaScript UI development because Mithril is overall easier to use, understand, debug, refactor, and maintain than most other JavaScript-based UI systems. That ease of use is due to Mithril's design emphasis on appropriate simplicity – including by leveraging the power of JavaScript to define UIs instead of using an adhoc templating system. Mithril helps you focus on the essential complexity of UI development instead of making you struggle with the accidental complexity introduced by problematically-designed tools. Many popular tools emphasize ease-of-use through looking familiar in a few narrow situations instead of emphasizing overall end-to-end simplicity which -- after a short learning curve for Mithril -- leads to greater overall ease-of-use in most situations. ..."

Two key points there are that React's setState(..) approach to minimize redrawing is a premature optimization (which then leads to wastelands of endless opaque boilerplate like Redux) -- and also JSX is completely unnecessary and counter-productive compared to just using HyperScript API to define interfaces in plain JavaScript/TypeScript without needing to introduce extra compilation steps or more complex tooling. Another key point is that Atomic CSS like Tachyons and similar approaches obviates the need for all kinds of specialized CSS encapsulation complexity. Mithril and Tachyons leverage the flexibility of HTML, JavaScript, and CSS without trying to reinvent too many other complex layers above them -- layers which typically just create more problems in the end via accidental complexity unrelated to actually creating UIs.

In general that analysis applies to most current JavaScript-based UI libraries. Elm (which perhaps helped inspire Mithril as a vdom) or ClojureScript or other similar tools might be exceptions though for people willing to put the time into learning those languages (which compile to JavaScript) and dealing with integration issues.

So, in reading the article and also much discussion here and elsewhere, much of that verbage to my mind fits into the category of seeing (yet again) inexperienced or otherwise constrained developers picking one problematical tool and struggling with it and then jumping to another one with different (perhaps lesser) issues again without having broadly surveyed what is out there or understanding key concerns like simplicity. Of course what is much more painful is working in organizations where such faddish choices are then forced on developers who know better (as is often the case, including sadly why I know so much about Angular and React even after years of experience using Mithril successfully).

That said, once a critical amount of time and money has been spend in getting developers to use a particular solution like React, then yes, there is the sunk cost which makes it easier for an organization to do other projects in it and maintain them. Just like why a lot of other legacy software persists...

Just like Facebook could promote React aggressively over alternatives (even when React had the problematical patents clause in its license), I'm reminded a bit of when Java overtook Smalltalk in part due to huge amounts of money pumped into advertising and promoting it (including by IBM, which ironically eventually had two good Smalltalks of its own).

Every tool has its strengths and weaknesses in different situations (including Mithril and Tachyons). And I can accept that broad industry adoption is a plus for any tool for availability of developers and third-party libraries. Still, it's sad for me -- after having implemented UIs for about four decades in hundreds of different ways -- that when I find something like Mithril that works really well for current needs and has (all things considered) great developer ergonomics and a great (if small) supporting community, it is mostly ignored. While Mithril+Tachyons+ES7 works differently than Smalltalk and related UI libraries, that combination makes UI development almost as fun as it was in Smalltalk -- but with broader reach because HTML+CSS+JavaScript is now everywhere. For good or bad, I guess Mithril will remain a "secret weapon" like Smalltalk used to be. :-)