macOS unable to open any non-Apple application

> How can launching apps be depending on a cloud service being available...

It's not, per se. The apps will launch if you block the specific subdomain, or turn off internet. The problem is if the computer thinks it can connect and keeps trying.

Ah yes - the “poor X is worse than no X”-problem.

It’s a huge problem on Windows where Explorer.exe still blocks the UI thread while it checks SMB shares if it thinks it can connect to them, but it skips them if it knows the computer is disconnected from a network. So using a Windows computer on a very spotty WLAN is actually more painful than being disconnected due to all the timeouts and dropped packets. Office Outlook is another main offender. I have a Windows Firewall rule just for Outlook.exe when I know it’s going to lock-up a lot.

It's like no one at Apple has ever had sporadic internet access and they don't plan for it. The Apple Music app does the same thing, if you are connected to wifi but don't have internet access it takes 60 seconds for a song to start playing every time you click one. Because apparently that is a reasonable timeout for a UI action

So, yes: they do depend on the local (to the user) availability of that service. So they depend on that.

No, they don’t! If the server is unavailable everything works fine. The problem is when the server can be reached, but is nonresponsive.

I think that’s an important difference. If Apple’s servers ever go offline, the OS will continue to work.