I think of Firefox containers (and Chrome "people") as providing a little isolation, but not enough. If I browse HN in a container, I'm likely to follow links to a lot of different domains. I'd have to diligently select the right container each time.

I'm suggesting instead the browser never mixes a cookie I was assigned while browsing say nytimes.com with a cookie assigned while browsing washingtonpost.com. Even if I regularly browse these domains in my "news" container.