I'm typing this comment from a notebook with 8Gb RAM and it is barely enough for a modern desktop - my system is running out of RAM from time to time (because modern sites are JS heavy and Firefox with multiple tabs sometimes uses all available RAM). I use i3 which has a small memory footprint and assume that with KDE/Gnome I will be running out of RAM more often.

If you have >32 Gb RAM you could ignore DE/WM memory usage but it is a relatively privileged position to be able upgrade hardware faster than software appetites rise.