Earlier quoted context omitted.
> Firefox has no profiles. Patently false. Been using profiles for years. > bunch of hacks, such as containers, which are cumbersome to use. Firefox's "solution" forces you to switch Github tabs between personal and work containers constantly. Rarely have I had to that. Until I added rules to open certain URLs in specific containers. > Chromium provides separate windows with different profiles, and Firefox should fol…
Firefox's "answer" to profiles is to run essentially two (or more) copies of the browser rather than only copying the profile-specific parts of each profile. This leads to a lot of wasted CPU cycles and RAM and is a very suboptimal solution compared to what Chromium and Safari do these days, not to mention that the ability to create and switch profiles is not included in the UI by default and requires an extension to…
Profiles do have a built-in UI at about:profiles or by launching Firefox with -P, neither of which requires an extension. Admittedly this UI is a bit basic, but a better version is being rolled out (https://support.mozilla.org/en-US/kb/profile-management). Running multiple profiles side by side does indeed involve running multiple instances of the browser.
Containers are an internal API and need an extension like Multi-account Containers to provide a GUI (though this is an official extension by Mozilla), however they don't require running multiple copies of the browser.