I have tested this and they are very capable, replacing the modern windows calc (38mb mem) with an identical app (ux, looks, features, accessibility, localization) ended up with an app using 2MB memory.
You just need to point it in the right direction (c/rust/go etc) and be harsh with the requirements, especially memory usage.
If I was Microsoft I would use AI for this rather than badly embedding AI everywhere, a lot of power users would be overwhelmed by a win 11 update where OS apps/features dropped mem usage by 90%+
It would be excellent to reduce Windows memory requirements using the very tools which are making memory so expensive...
Oh wait no that would be incredibly painful for everyone. Yes reducing memory requirements would be great but not at that cost.