Development in languages like that used in GNOME, or modern windows are faster & easier (with theoretically fewer security concerns as the language provides bounds etc validation at cost of speed) than older more traditional languages (the coder usually wrote field checking but this varies with language).
However if you want a lighter DEsktop, just use another one. Whilst some more recent GTK+ ones too have become heavy (GTK+3 is heaver than older GTK+2), they do vary & use less than GNOME. MATE, Budgie & XFCE are lighter (older XFCE was very light, but with move from GTK+2 to GTK+3 it's somewhat heavier now too). The lightest in the GTK camp is LXDE (being GTK+2 and used in Lubuntu up to 18.04 LTS)
Across the 'pond' (ie. in the Qt camp) there is KDE which is much lighter now (Qt5 uses considerable less resources than did Qt4) , but if you want very light here use LXQt (Lubuntu 18.10 & later).
I was testing Lubuntu [& Xubuntu] 19.04 on a dell d610 & ibm thinkpad t43 & like systems (ie. pentium m, 1gb ram) until last month when x86 daily-ISOs were stopped. Just because GNOME is heavy, we still have other choices (including alternative methods to install Lubuntu/Xubuntu given x86 ISO's are no longer produced!)