I hear a lot from linux users that found gtk 2 era on x11 as pretty close to perfect. I know i had run ubuntu and after boot it used far less than 1GB. The desktop experience was perhaps even slightly more polished than what we have today. Not much has fundamentally changed except the bloat and a regression on UX where they started chasing fads. I suppose the most major change on RAM usage is electron and the bloated…
Most of the bloat these days is from containers and Canonical's approach to Ubuntu since ~2014 has been very heavy on using upstream containers so they don't have to actually support their software ecosystem themselves. This has lead to severe bloat and bad graphical theming and file system access.