It's weird how people always complain about lack of easy profile switching in Firefox. If one tells them that what they are really looking for is containers, they dismiss containers, but then proceed to complain that profiles don't have the same features. If you want sync across browser instances, manage them with one Firefox account... You really want containers not profiles.
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 a…
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.