xtrox
Browser addons only isolate sessions by having separate containers for cookies. The tabs still share the same process memory space. So if you have a malicious webpage, and a vulnerability in the browser, it might be possible to get info from other tabs. That's the problem Vanadium and other Chromium browsers try to solve with their site isolation. Each site is run in its own process, and thus memory is isolated.
https://www.chromium.org/Home/chromium-security/site-isolation/
Firefox for Android doesn't have this yet, although someone claimed to have it working.
https://www.reddit.com/r/firefox/comments/ttn9oy/site_isolation_is_working_on_firefox_android/