Like 10% of Steam is yum/brew. The other 90% is:

* GUI

* managing installations, including things like Proton to run Win32 games on Linux, and Fossilize to precompile shaders

* bandwidth-saving stuff like being able to transfer games locally

* being able to play remotely in a variety of configurations: LAN, WAN, or having a friend connect to your local session ("Remote Play Together")

* pretty good support for mapping any controller you have to any controller inputs a game wants

* cloud saves

* a bunch of community features like forums and broadcasting

* family sharing

* a VR runtime

* marketing for devs (regular sales, algorithmic recommendations etc)

* an API for devs with various services

* the backend infrastructure for all of the above

It's been around for a long time so it's quite feature-rich at this point. Lots of things that generally make sense to have.

and telemetry

Similar to Google Play with Google Play Services: both an app store and a set of services for games to use

More like an app store, which is really just a GUI/payments/licence layer on top of a package manager.

Yes; but more like the apple App Store - they take a cut, and (to some/varying extent) try to ensure some level of legitimacy / quality.

More like flatpak/flathub since it has it's own runtime, with the addition of community features and purchasing.

more like an app store

Yes, and also a store and a community platform.