They're not [always] about hiding loading times. Even switching from an app to the desktop screen has a slow animation, or switching back and forth between two running apps.

That explanation makes no sense in this case. The workspace transition animation takes a full second, on extremely performant devices that can keep up their pace up until the OS swaps around 15GB, at which point animations start lagging so they actually make it even worse. Meanwhile a Linux setup will switch workspaces instantly. Same for Windows 11 if you turn off animations, by the way.

This animation slows every transition by one second including entering and leaving fullscreen mode, because on Mac OS fullscreen works by moving the window to a new workspace. There is no justification for this.