Experience is still lacking compared to Chrome profiles. Chrome profiles are so much better UX wise than any other solution, especially the color coding of the window.
I want ONE window with all my tabs, in a vertical List (tree Style Tabs and/or Sideberry) which is another feature Chrome lacks completely, it implementation of Vertical Tabs is TERRIBLE
And you can edit the shortcut to ask you which profile you want to use when you start Firefox.
This opens a new window with that profile, but you can switch between each window at will.
The lack of discoverability of that "about:profiles" page is indeed a UX issue compared to chrome, but other that that it works pretty well.
For most use cases, I find the more lightweight multi-account-containers more useful though.