I found container tabs to be useless for my use case:

I want to have two YouTube accounts running simultaneously - one for entertainment and another for coding/AI/science. That way the YT recommendations in both accounts diverge to the different use cases. Using two Firefox profiles was the only way to do this.

I would be very disappointment to see Firefox profiles deprecated.

Minor nitpick - the poll options should say 'yes I use profiles' not 'yes I do'. Same with the no option. Be clear to avoid confusion.