You also often need several tiers of pausing. For example when paused you want the current game time to be zero, but you also want to ignore only some user inputs. You don't want to disable the menu or pause/unpause actions along with player actions, also you might want to pause dialog but not music (although you might alter it for the menu).

Then there are others such as vfx that can have their own tiers, you might have something in the background that is difficult to pause, stop and/or resume.

Then there are other things such as timers etc. that will need special handling, graphics card interactions etc. When done with those you also need to be able to resume and ensure that all of the previous will continue as if nothing have ever happened.

In the same vein some other "simple" things like saving/loading the game is often anything but.