The open source UIs initially seem alien, complicated or obscure related to similar to closed-source Windows' ones. The reason is OSS projects are built by developers primarily FOR developers and not for regular users. The design principle of "Don't surprise me" and other artistic and ergonomic ones are not met. Examples are Gimp and other content editors like Handbrake, Firefox vs chrome in mobile only, even IDEs.
BUT with time and a variable effort a regular user can get accustomed to the new philosophy and be successful. Either by persistant use, by using different OSS apps in series or by touching the command line. Happy user of Firefox, Libre office, Avidemux, Virt-manager (sic)
replies(1):