I'll agree when PopShop doesn't take 800mb of ram idle in the background (it keeps the entire repo in memory instead of in a DB).
Is it a matter of these particular bits not receive adequate attention or something else? I'm not opposed to trying to pitch in and help improve them but before that's feasible the root problem needs to be understood.
I think a lot of it is because distros tend to play hot potato with the packaging and try to reduce their load by building off Debian or Arch, which makes the experience way less consistent as you end up with fragmentation surfaced to the user. Add in a bit of corporate open-source "embrace the user" and you get app store jank that the developers never use because they just open a terminal instead.
I'd fix it myself but it's all in Vala and I don't have time to learn another language.