Firefox's Container's approach has been quite interesting to use, but if a suggestion could get out to the Firefox team, I would advise improved streamlining of workflow for the extension, including with sync and returning browser setup, and for organizing and setting up new containers (configuring them to always open for a domain, putting them in folders).
With Temporary Containers, you can easily run one new container per tab. Or one new container per domain or even subdomain within the same tab. Although the latter option will break many sites and the go back button.