Re: *Spoilers* Problems caused by the MCU
I didn't like Iron Man because it was grounded. I liked Iron Man because the characters behaved like real people. It doesn't matter how fantastic the threat is. As long as your characters have a realistic response to the fantastic elements, its fine. This goes for Nolan's Dark Knight trilogy, too. It isn't realistic at all; the characters simply respond like real people would to the events of the trilogy.
"I am for no master nor moral persuasion. I am for myself. What your yearning soul, madam, might mistake for loyalty to person or Purpose is merely a firm and, aye, principled determination to accept responsibility only for myself and my own actions." - Elric of Melnibone, The Revenge of the Rose (Elric: Swords and Roses).