I ran the demo site (https://rustmart-yew.netlify.app/) through Lighthouse and got the following results:

    First Contentful Paint    2.3s
    Time to Interactive       2.3s
    Largest Contentful Paint  3.9s
    Cumulative Layout Shift   0.42

All numbers are coloured orange or red, so even Google isn't a fan.

That said, 2*760ms of loading time comes from Google Fonts and Cloudflare's CDN for normalize.min.css. Were those hosted locally instead of on two useless CDNs, the times would probably almost less than a second, which, depressingly, is considered acceptable these days.

WASM typically has very good startup time only because the binary WASM format is so much faster to parse than javascript. See js-framework-benchmark, "Consistently interactive", Yew even beats vanillajs by about 4%.

https://krausest.github.io/js-framework-benchmark/2022/table...

Having said that, I still wouldn't try to use Rust as a React replacement for other reasons. Maybe in a few years.