Iron Man is nothing like Batman lol. Why would he ever replace him.
While you make great points it's still important to remember that most of the general audience does not analyse storylines and characters this way. If you were to ask someone why they liked Batman they'd reply with ”He's cool and dark and has no real powers”. That's about it. This description fits Moon Knight as well. A successful Moon Knight movie would most definitely stunted Batmans gross. Same way Namor, if ever made, will be damaged by Aquaman.