[SippinLean]

>It looks "old" and out of style

You mean the default theme for 3? Eh, ok, make your own. I've never used the default theme.

>browsers support a lot of cool css features which a lot of times makes these frameworks useless

BS4 integrates these technolgies? I could write all my components using flexbox from scratch, but why would I when BS4 already has them?

>Bootstrap is the jQuery of CSS

The mixins, functions, helpers and utilities?! What have you replaced them with?