Just use Phoenix and live view.

Prototype is easy and fast. Scales well to very large user base on a single node. Interactive client side without even writing JS.

I love rust, I really do, I use it for all kind of things. But for web app, the Erlang architecture is so well designed and mature you cannot compete.

Also we use rust and zig from Erlang with native modules for video processing and AI, the elixir/Erlang "skin" gives you immense flexibility and productivity with almost no performance hit.