That’s an interesting opinion as react, Vue, svelte are all in favour of having css and templates together with js. What do you prefer?

IIRC, Vue allows you to move link to a separate html,css and js file from vue sfc file should you want it

You are right, I prefer exactly this - to separate CSS, HTML, and JS/TS.

I know that “smaller components are better”, I agree with this rule, but I prefer to draw the boundaries myself, not forced by the capabilities of my code editor.

It's one of the things I love about svelte. Obviously global styles live in a separate place, but having scoped JS/CSS alongside the HTML its related to is a godsend, especially as a project grows.