[onion2k]

I'm seeing 714kb of data loaded over 924ms.

That's not the React stuff though. There's 82KB of JS from the React bundle (main.08bdff3a.chunk.js and 2.8a9031d8.chunk.js) on the demo site (plus 18kb that's loaded asynchronously for Google's analytics script). Everything else would be necessary even if it was static HTML and vanilla JS. Heck, the video-placeholder.jpg image is bigger than all the JS combined.

And it's not really been optimized at all. A whole stack of the React components could be lazy-loaded with Suspense to get the initial page weight down a bit more. If you didn't want to do that you could probably swap React for Preact and knock another 20KB off the JS bundle size.