I have no idea what you are talking about. XFCE is absurdly easy to theme with the settings laid out and applicable in each area. It allows and offers more extensive theming than Gnome does - By Far.There is literally nothing about it that is PITA by any measure.
Reading that statement, for me, was like reading someone say "It's a real pain to drive a car unless Tesla does it for you."
Blew my mind.
It seems an unfair statement to dismiss Mint, Zinc, MX Linux, Zorin OS Lite and all other XFCE distros because you did not like the default look of One Distros implementation.
Gnome ties the user up and disregards the users will to customize their workbench far more than Microsoft does.
I feel less controlled by Windows than I do by Gnome.
Gnome won't let you right click the panel (taskbar) and make any changes to it whatsoever. Gnome won't let you keep icons on the desktop - at all. Gnome won't allow multiple windows - it requires that your windows open as minimized by default - you have to change that setting. It hides many settings from the Settings GUI apps and you must use a Gsettings command to act on them. Gnome disallows scrollbars and toolbars and hides everything behind hamburgers. Other Developers have to do all of the work Gnome removed itself from and put that stuff back in. Other developers must restore functionality by independently developing Extensions.
And Gnomes response? "Extensions are a niche thing and on the way out."