I was quite frustrated by this as well, but then I remembered that the design goal of the extension is allowing logging into the same service with multiple accounts, not isolating services from each other. That is why the secondary functionality, the possibility of isolating tech fiefdoms, is less polished. It's not the main show, it's just a happy side effect.
Containerise and Cookie Autodelete together are indeed a very good addition to uBlock and uMatrix, and if you already have some Regular Expression classification rules written for Cookie Autodelete, setting up Containerise is very quick. It works like a charm even with the Firefox Multi Account Containers extension itself disabled.
Containerise and Cookie Autodelete together are indeed a very good addition to uBlock and uMatrix, and if you already have some Regular Expression classification rules written for Cookie Autodelete, setting up Containerise is very quick. It works like a charm even with the Firefox Multi Account Containers extension itself disabled.