Comment by jetin
Yeah, I also used the Shadow DOM a lot working on a CMS that edit the website content “in place”: CMS UI was safely scoped inside my web components thanks to their Shadow roots, I never had to worry about arbitrary styles from the websites the CMS was loaded in colliding with internal CSS.
Shadow DOM exists for some specific use cases but it shouldn’t systematically used when creating web components.
I actually think shadow DOM plus CSS import assertions are an incredibly good combination and make it totally suitable as a sensible default.