Even with an editor like Age of Emire, 'craft or C&C it takes alot of work to make a good mission. I think a spring mission on that level would almost be as much work as a complete game, considering you have to build/tweak the tools first.
It is not about that though:As for good maps that noone plays that is a hard question to answer as I try to play the good maps when I can remember them.
For new/casual players it is hard to find good maps.
No *a game has a mappack or a maplist (some outdated pages on wiki do not count, nobody reads those)
Ok, zk has planet war which brings some rotation at least, I think.