There is a ‘half’ workaround for this listed here reference another mappable key command for a more traditional (but not quite) pause option:
The reason it’s called “Active Pause” is entirely that - everything remains active except for your aircraft position, and I presume it allows you to adjust your avionics etc. which can be useful for learning & practising during a busy approach etc.
I also see the value of a true pause, but I wonder if they took this approach to avoid trouble with some of the multiplayer aspects. For example, if you use “Live” mode I believe you’re locked to using real world time. This is the option that says it gives the most authentic experience. How then should the game respond if you pause it mid-flight? Your in-game time will start to fall behind everyone else’s; maybe that has implications which we aren’t aware of yet. These are my thoughts as a new user anyway. I don’t have the experience of the Alpha/Beta testers.
I hope we will see a simpler/clearer approach to the pause options in future, even if it somehow differs by the ‘online’ mode selected, but I’m sure there are some reasons for their design choices.