about:profiles isn't that bad. There's no reference to it in the UI though.
Similarly, -ProfileManager has existed for ages and that experience is also bad.
If I have to go to the lengths of about:profiles or using the -ProfileManager or -P command-line switches, why not just sandbox the entire thing?
It definitely needs a useability upgrade.
I've never had any issues typing "about:profiles" into the URL bar. It even autocompletes.