We've had about:profiles for many years, but that UI is not for the average user.
On macOS opening a new profile through that also opens the window in the background and may also mess up your Firefox icons in the dock, not to mention that you'll break your profiles if you make the mistake of opening a profile from a different FF version on your current FF (eg: stable profile on FF Developer can't be opened again by FF stable). We can use profiles, but it's not a good experience.
On Chromium (and Chrome, Brave, etc), there's an icon at the top right corner. You click it, then select the profile and that's it. Fast, simple, user friendly.
(Edit to add: I sometimes forget that the average HN user is different from the average computer user. They're used to click on things, not to type "firefox -P" :P )
I've used that before. Props to the developer, but on top of the extension, we also have to install software for it to work. It also doesn't fix new profiles opening in the background and the messing up of dock icons, although this might only affect Mac users.
The annoying thing for me is that Firefox already has a similar UI button that could easily be adapted to switch profiles. It even looks like Chrome's, but all it does it show you your Firefox/Mozilla account.
It's designed like their goal was to make the few buttons you want to use most the hardest to find.
I'm not going to the profiles page to restart Firefox, show my profile directory in Finder/Explorer, Rename a profile, or Remove a profile. For some reason all those buttons get first placement.
I have to scroll the page down to find the one and only button I want to click every single day.
(Though I still use it out of muscle memory. alt+F2 firefox -P is so quick to type.)