Are you setting this option to something else?
Temporary Containers works really well for me. I have per domain isolation, which only breaks very very few sites (Gmail and Outlook 365). For those I have regular persistent containers. Alternatively, I can always open a new private window where I don't have this plugin active.
uBlock Origin + Temporary Containers + ClearURLs are a great setup for privacy and security. Actually, I don't need much else aside from a VPN and a few settings in my user.js.
The only thing I miss is Vimperator. Modern alternatives are full of glitches because of inherent limitations in the WebExtensions API.