Virtual DOM is pure overhead (2018)

On their machines.

That's often a critical distinction. Developers often get the nicest computers, and they often get to have good, fast Internet connections that are close (in terms of Internet topology) to the server where the site is running. So they can't necessarily perceive the effects of the browser being starved for resources, or jank from the app being chatty over a high latency connection, or resources failing to load due to a spotty connection, or anything like that.

What some of these technical decisions add up to is situations like a family member who's using a cheap Chromebook and has flaky Comcast cable internet, bewilderedly asking me why this site they're trying to use keeps showing them a blank page or somesuch. They know that, if the page doesn't load at all, the browser usually gives them a, "We couldn't load that page. Try refreshing," error. What they don't get is that, if it's a React app and some JS resource fails to load, it'll stop the rendering of the site cold, and they'll just see a blank page, or a half-loaded page, or some other confusing state. And I've yet to figure out a way to explain things to them that gets them to see this as, "The Internet is being flaky." They see it as, "Your site is flaky."

They're not entirely wrong about that. The people who develop Internet and Web standards have put a lot of time trying to engineer the Web to tend toward failing gracefully. React (and frameworks like it) seems to have, in one stroke, undone all that and instead engineered things to tend toward failing catastrophically.

I don't know if you could get a JS-first framework that doesn't behave that way, so maybe it's a necessary evil? But, I get that React solves a real problem that some people have, so it'd sure be nice if it weren't.

Sorry to pick on this point but depending on your application this should be more (or much more) important. Too many teams have this same opinion and it's glaringly obvious how little they care about performance. I'd agree that raw performance isn't really important, but the ways you can and the tools you have to optimize the performance of the app are if you find that you have bottlenecks is and this does partially depend on the framework.

That said, I would agree, all frameworks would probably be fast enough for most use cases, and even with the optimization aspect arguably the most important aspects are about application structure and how the framework forces you to structure your application. As you mention, I think this is why React wins, the way it forces you to think about things unidirectionally, think about state and components separately, etc. are all big wins for understanding your application.

Also worth noting is that Svelte doesn't really have a big company backing it like React does and so the ecosystem is smaller, which could contribute to its relatively small size.

Which browsers do not support natively for decades and entire markets of ecosystems grow to work around that stupidest fact. Browsers could detect, batch and “reconcile” (whatever that means) the changes to the js runtime with much less runtime and devtime overhead than it is done in js by manual state tracking and updates.