“Why We Didn’t Use a Framework” (Case Study) (smashingmagazine.com)

I am sure this works really well for apps with minimal UI as it is the case.

I agree with a lot of this: the developer productivity and page load performance gains can be drastic.

But I think it's weird to make a claim such as "we made our web app small in size because we need network bandwidth and CPU power for video streaming"

Frameworks for JS UI rendering have a potential to actually improve CPU usage by leveraging various techniques under the hood to minimize repaints. Using "heavy" frameworks can actually improve page performance.

Also, doesn't the JS bundle size pale in comparison to video and audio bandwidth?

I'd like to see how using React or Angular can affect WebRTC performance.