When you understand this, React's shadow DOM and JSX are completely unnecessary.
Combine it with the fact that grid layout is expected to be in the stable releases of Chrome and Firefox in the next month, and, if you have no legacy browser requirements as I happen not to, web application development becomes somewhat reasonable for the first time since I began doing it in the '90's.
Admittedly, when I started trying to build a library out of this (https://github.com/madhadron/allorryll), I put it in TypeScript, but I'm also the guy who did serial port and Firewire camera control in Haskell.
Obviously this doesn't apply to writing documents on the web, where JavaScript should only be added as part of a structure that will gracefully degrade.
I agree that web development has never been more fun that it is today, except for Safari with buggy flex implementation and iOS that set position: fixed to absolute and refuse to properly scale the "document" when you want to type some text. Every time I get a bug report these days it is Safari or iOS that doesnt follow the standard. Chrome, Firefox, Edge works great most of the time.
ES2016 is "plain JS".
If by "plain JS" you mean "jQuery plus ES5", I encourage you to learn what's happened in the last half a decade.
The irony with all these frameworks, in many cases especially for small projetcs, it will be more efficient to code it from scratch than dealing with the whole stack thing. So much for not reinventing the wheel ...