They already are separated, in the sense that you can, and people do, embed Chromium-powered webviews in custom apps. I don't know if the particular app you're

They already are separated, in the sense that you can, and people do, embed Chromium-powered webviews in custom apps. I don't know if the particular app you're asking for exists, but there's no fundamental reason why it couldn't be built. (Having to re-log-into everywhere on every new session sounds like a nightmare, though, especially with phone-based 2FA, which unfortunately is still the best that most sites offer.)