Comment by fmnxl

You'd need to re-invent the wheel on so many things.

Flexbox layout? CSS animations? Some custom npm library that I need to use to provide social logins, SDKs to integrate payment gateways? etc etc

If all you want is just a set of UI components, sure. We already have plenty of UI libraries out there.

These days there are many better ways to write low-JS, low-boilerplate code. HTMX for interactivity, UnoCSS for generated CSS on the fly. It's even possible not to bundle your ES6 modules these days, with <script type="importmap">.