In what way viable alternative? JS performance is pretty good if you think of an admin interface or any business dashboard UI full of charts and stuff.

React for example shifting towards functional programming makes FE apps simpler and predictable.

If you dislike the HTML/CSS UI layer then WA is indeed an alternative. However you need to reimplement everything, like text selection, right click, focus, accessibility, dropdowns, etc, because all you have is a <canvas> to draw on.

But! WA will eventually have DOM access, that will definitely open up the landscape to create new frontend frameworks.

There are already several libraries that allow you to write React-like SPAs in the browser via WASM.

The two largest are Yew (Rust), Vugu (Vue-esque but with Go instead of JS), and Blazor (C#)

https://github.com/yewstack/yew

https://github.com/vugu/vugu

https://github.com/aspnet/Blazor

All are perfectly viable for production apps as of today and not much more difficult than writing React, given you have some familiarity with their implementation language.