Comment by cycomanic

Just FYI temporary containers (Firefox extension) seem to be the solution you're looking for. It essentially generates a new container for every tab you open (subtabs can be either new containers or in the same container). Once the tab is closed it destroys the container and deletes all browsing data (including cookies). You can still whitelist some domains to specific persistent containers.

I used cookie blockers for a long time, but always ended up having to whitelist some sites even though I didn't want their cookies because the site would misbehave without them. Now I just stopped worrying.