It isn't immediately obvious, but if you haven't saved you can save your status and then restart from the beginning with all your experience, so it's not like everything is wasted.
As for what you're missing, the zombies themselves aren't that hard, but if you try taking the most daring and impressive pictures it creates its own challenge. Also, there's simply the fact that as you play stuff happens around you, it really feels like a living world rather than one that tries to simulate it assuming you'll follow the steps the devs set out for you.
As for what you're missing, the zombies themselves aren't that hard, but if you try taking the most daring and impressive pictures it creates its own challenge. Also, there's simply the fact that as you play stuff happens around you, it really feels like a living world rather than one that tries to simulate it assuming you'll follow the steps the devs set out for you.