> Some of its advantages are, in a sense, unfair, because it doesn't manage my OS or its most vital pieces[.] [...] [T]hat's totally fair if you consider the platform as a whole. It's really hard for Linux overall to separate user packages from system packages, mostly because it's all mixed up together in a way that it's not on MacOS or Windows—but a distro could take that approach, if they wanted.

Yeah, this is a valid insight! It's essentially the approach that contemporary free BSDs take, and it's a direction popular distros are gradually trying to move in by shifting end-user applications to containerized package managers like Flatpak, AppImage, and Snappy. Fedora Silverblue is an example of an extreme case, where the base system is read-only.

> #1: Separation of a very complete and capable base GUI OS […]

I suppose the BSDs fall down here, since their base system doesn't include a GUI.

> Every other package manager I've used for any serious length of time, I've repeatedly seen get in weird states that required substantial fiddling before I could use them for anything again, after what should have been boring and normal usage.

I've only really seen this happen when using distro package managers to perform several years worth of release upgrades or convert between distributions.

I like the uniformity of Linux's package management tools (i.e., the ability to use the same tools to manage OS components as end-user software), but I can see how using one thing for OS components, especially if it's reliable and mostly hands-off, but then using something else for end-user software can be appealing.