Red Baron was far from perfect, but that part of it was excellent. You never knew what you were in for on a mission, even from campaign to campaign.
Not only that. For me one of the most important things was the open end of your missions, just like in real life. Sometimes you rule, sometimes you will be chased back to your aerodrome. But no matter what, unless you died there was always a new day with a new mission.
I was thoroughly demotivated by "campaigns" in other sims where you had to fulfill partly absurd (compared to RL) requirements to carry on, or you were forced to replay the thing. A great battle, 3-4 bombers shot down under adverse circumstances, you barely make it back to your base, but ready to fight another day - do you get a medal? No, "mission failed, try again" because you did not kill ALL the enemy bombers
I was far more happy with one or two kills but adding another day of "survived" to my RB diary. (Now you all know where my AH play style came from
)
I don't think I had ever completed a full campaign in the original EAW or Il-2 releases...