I had to abandon XFCE due to some issue with aging XFCE4 libraries and high cpu problems, switched to KDE Plasma 5.x,. got 50% longer battery lifetime and havent looked back.
They need to focus on these kinds of problems, not on adding new features, otherwise I would have stayed.
what about a DE's libraries would make it drain so much battery life?
Does xfce do a lot of the graphics in software? That is very inefficient on modern hardware.
It might be that they are not interested on "Market share". Or they are but not enough to justify the work. I'm sure they would be glad to accept a pull request.