I'd agree with that. It's simply a matter of becoming more of a perfectionist as you get better. At first you just throw some ships and events in there and think "Hey, this is a pretty cool mission", and then proceed to play it and enjoy the explosions. Later you tend to think "Decent... but I think this briefing icon is off by a few millimeters, I could use some more wingman chat during the lulls, and maybe a few bonus goals for dedicated players to chase. Oh, and the background needs to be completely redone to suit the mood of the campaign".
Takes forever to finish once you start nitpicking your own missions.