But is any of this really an issue?
XFCE was/is a ‘lightweight’ desktop mainly by virtue of the past.
These days its gotten heavier, while the ‘big ones’ have gotten ‘lighter’.
Sure … but that has to do with DE development itself … as well as configuration.
(as you note above … you add conky and its heavier … though your difference seems to indicate some sort of misconfiguration … conky shouldnt take much more than a few megs maybe … which is again, indicative though of the impact that your own configurations can make)
That all said … aside from things that are really unnecessary, like weather widgets (again user choice) … we do all roughly end up at the same point plus or minus a little. My KDE is somewhere in the 400mb range. XFCE can be as well. Certainly Openbox and other WMs too. But we could also add enough to openbox to make it 600mb+.
And still … in the end … what is a few hundred mb one way or another?
Is it actually even wasted, or is it cached?
Open up chrome with 1 or 2 tabs and it immediately eclipses your entire desktop with its resource usage.
Honestly chasing the lowest possible RAM use on a desktop is itself largely a relic of the past (and windoze), unless you have specific hardware or other situational constraints.