I recently started using firefox and was very frustrated with how large the UI was, how it autofilled entire URLs while i was trying to search something, and how it changed my system's titlebar buttons (minimize, maximize, close) to windows ones when I changed the theme from the default. I just found out about about:config and was able to solve every major issue i had with firefox literally within minutes, so why do they hide most of the settings?
it makes way more sense to just put the settings in the settings menu. also, why hide the compact density option? on a 1920x1080 display the default is about an eighth of my screen, my taskbar is only like 60% of that. having tried a couple of firefox-based browsers, i can confidently say the only thing any of them do better (aside from telemetry that can be easily turned off) is their settings. why does firefox hide most of the settings?
the telemetry doesn't reflect accurate use of 'advanced' settings, because those users have already turned that function off.
A subset of "advanced" users might have turned telemetry off so it certainly is skewed somewhat, but I don't think there a good reason for me to believe that the subset is necessarily that large.