Maybe you just don't understand the difference between containers and profiles, or what is it about profiles that's useful and more useful in some cases over containers. For one, it's impossible to have separate extensions with containers. That alone is already a deal breaker, and there are many more differences. Profiles are useful when you want to have things to be actually separate, not just pretending like they are while they're all cluttered in the same profile. It's also about more completely eliminating risk of having something where it doesn't belong.
It's kinda tiresome to see containers get peddled over and over as a "solution", when they're severely limited in what they offer compared to profiles. One feature set and clunky interface doesn't even get close to the use cases people have for profiles. It's not a solution.
So use profiles for what profiles are good at, and containers for what containers are good at. This works well for me.
I have a work profile with several containers inside, so that I can be logged into, e.g. GitHub and AWS, with multiple accounts at the same time.
I also have a primary personal profile, with a few containers primarily for cookie pollution separation.
I've never struggled with the "Profiles have bad UX" complaint, because I created a few different launchers for Firefox: work, personal, (a few others for special purposes like retail sites), and a default profile that launches the profile manager dialog at startup so I can select from a few dozen less-frequently-used (sometimes single-purpose) profiles. I like to keep separate things separated.
This took 20 minutes to set up, 15+ years ago(?) and has been perfectly convenient for me, but I've also recently read that Mozilla is working to improve profile switching.
Selecting a profile at launch has never been a problem in Firefox. Switching to a different profile in a running browser is prettier in Chrome though, sure.
The bigger problem for me is that (at least when I last tested Chrome profiles -- it's been a while), there was some browser config that was shared between profiles. Maybe extensions? I don't recall.
This was unexpected and undesired, so I went back to Firefox.
That depends a lot on the platform. On MacOS, for example, switching to a profile from about:profiles results in the new window being open in the background and it would mess your Firefox icon on the dock. The solution used by Windows and Linux users (the -p command) also doesn't work here (maybe it does via the terminal, but not with shortcuts).
Anyway, there's no benefit to Firefox or its users if profile switching is ugly or clunky. They're improving this and that's a good thing for everyone.
On macOS, sending `--no-remote -P <profilename>` in the command line is the method for launching specific profiles.
I add an icon (slightly modified for each profile) to the script, and rename it to (e.g.) ~/Applications/Firefox-work.app for convenience. Works from the Dock, Finder, Spotlight, etc. I usually launch from the command line, but all the usual ways do work.
Improving the profile switching experience is great of course. But the above workaround has served me perfectly for as long as I can remember. Obv would not work for everyone.
It's kinda tiresome to see containers get peddled over and over as a "solution", when they're severely limited in what they offer compared to profiles. One feature set and clunky interface doesn't even get close to the use cases people have for profiles. It's not a solution.