This is the same issue that was raised practically since the inception of Careers in the sim. Each mission has a secret trigger you have to accomplish in order to complete the mission. If you don't meet the trigger condition, you must refly the mission indefinitely. For whatever reason, this has never been changed. The mission brief may give you a clue as to what the trigger is, but for others you can fly it over and over again and never 'complete' it.
It sounds like you are talking about the Campaigns rather than the beta Career in RoF. You can't progress to the next mission in the Campaigns until you complete the objectives of the current mission.
However, in the beta Career (and in Pat's CG), you do not have to complete any objectives to move on to the next mission. In the beta Career you do have objectives and can see a Success (or other) message based on achieving those. Regardless of the outcome, you can fly the next mission (well, unless you die or get captured). As Pat points out, his missions don't have objectives, so you can always fly the next one there as well.