Career missions are supposed to offer infinitely different replays because they’re randomly generated, whereas FSX scripted missions offer a few hand crafted experiences that don’t change.
The irony is that that the randomly generated career missions are so tightly constrained in their parameters, and always use the same details and procedures, such that they wind up all being exactly the same, except the backdrop changes. Now you’ve got the worst of both worlds: the missions feel generic like they were made by AI, and they don’t have any variety, like you’re playing the same handmade mission over and over again.