Why don't we have complete main domain isolation as an option? It would work like containers, but they would be automatically created for each domain you visit.

Go visit youtube.com and anything loaded from that page is in the same container.

You'd have to log into each google property as the sites would be separated from one another, and there would probably be a need to merge these containers if say www.example.com and example.com are the same site (or automerge if there is a 302 redirect).