QT and a JS framework are used in very different contexts. If your toolkit is aiming to work on Windows, MacOS, and Linux desktops, it is directly competing with QT, GTK, and Native (on all 3, and very few apps do separate native UI). Open source works better with a larger user base, so aiming for "Window, MacOS, and Linux RUST APPS" is terribly restrictive on the number of people who will use it and hence maintain it.

I'm all for RIIR but it will take 30 years before enough has been rewritten for a Rust-only GUI to be viable IMHO.