The problem is discoverability and UX. I believe, in chrome profile management is another menu option. In FF you have to use about:profiles or start Firefox with a specific command line argument.

Unless you know about it or are actively looking for the feature, there's no way to know. If you are coming from Chrome, this unfortunately leaves the impression that Firefox doesn't support profiles (a must have feature for some).

It doesn't even hint or show up in settings search. It is as if they don't want anyone to use/know about profiles.