You could never officially choose system colors in AOSP. It was always white with teal accent. If you’re thinking of Substratum, that was kinda an unintended exploit when Google was working on adding native theming for OEMs.
Volume buttons are being made more customizable in Android 15, which is launching on Pixels soon.
Privacy settings have never been reset for me, maybe you’re confusing it with Windows 11.
YT music does have a problem with reuploaders stealing revenue through “topics”, Upper Echelon made a video about it a few weeks ago