Do you have any advice for developing this way? I've found myself too sticking in the VanillaJS camp, but not being able to talk about React seems to dissuade potential employers.
My only advice would be to stay consistent, find patterns and genralize stuff. I do see the irony of making a framework of my own in the process of doing all that. I just embrace that. Everything is exactly how we want it and we know each line that executes on the machine. Makes development a breeze. There is nothing that react can do that vanilla js can't with reasonably same amount of effort. But stay open-minded. What helped me was that I worked with angular first to see how not to do front end (angular.js). I also regularly check out how react, angular, Vue, etc handle the same problems that I have. That usually gives an inspiration.
In the end it's hard to believe how fast JavaScript can be even on smaller devices.
I agree with you and I do most of my stuff in vanilla JS these days, but if I have a complex UI state it can be nice to have a DOM diffing library rather than tracking and editing nodes explicitly.
Mithril is, in my opinion, React done right. The entire framework is contained in four methods. It doesn't have any awkward leaky abstractions like Angular, and it is super light and responsive.
React is a great abstraction, but some projects abuse the virtual DOM concept and you end up with a lot of unnecessary reconciliation (VDOM diffing) going on that slows components down.
In the end it's hard to believe how fast JavaScript can be even on smaller devices.