In theory that sounds nice but in practice i haven't seen a single desktop application that can actually handle resolutions lower than whatever resolution the developer/designer used. I used a 1366x768 monitor for a long while ~3 years ago and everything looked both gigantic and had padding everywhere.

As for the web, responsive design was so great that in almost every site i had to zoom out to make it think i had a monitor with a bigger resolution than i really did.

These days and since i do not maximize the browser (because my monitor is huge - like all modern monitors that do not have awful image quality tend to be), i often have to resize the window because sites tend to think i'm using a mobile phone and instead of scaling down / hiding less important stuff (that would at least be appropriate for a narrower viewport) they make thing ultraginormous (because touch screens), overly padded out (because touch screens) and they hide all options behind a hamburger menu (because mobile screens are physically too small).

I'm certain there are theoretically ways to do it "right" (a friend web developer told me how but i forgot) but absolutely zero sites (that i visit) do that.

And it introduces new failure modes. I often experience responsive web applications hiding UI elements in my Firefox windows. Those windows usually use either the left or right have of a 28" 4k display. Why the heck do the hide the sidebar to save space? It is fucking annoying.