I think one of the most accurate things said about current day flight sims is that they are wonderful to play while you are inside the cockpit but they are dull as heck when you are outside the cockpit.
The one I rally noticed this on was when Rise of Flight first released. The planes and flying were awesome. Most single missions were also well done.
But, outside of your mission there was nothing. The whole beautiful map looked good for just flying but was so empty and clinical. Only your flight and the enemy flight would spawn. Maybe bombers if it was an intercept or escort, and then the ground targets for it.
The WWI flight sim I played before that was Red Baron 3, there were loads of aircraft all around. If you went off the mission and hung around an enemy airfield, they scrambled against you and it seemed there was an actual world war going on.
And another note: What I hate most about scripted campaigns are the stupid and unrealistic goals they make you meet. Like, shoot down 20 bombers, well, that's just impossible with realistic ammo loadouts. Even with unlimited ammo it's still outrageous. I think Microsoft Combat Flight simulator had a few of those.