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 never asked for this crown. Gold is cold and heavy on the head, but so long as I am the king, I have a duty … If I must sacrifice one child to the flames to save a million from the dark … Sacrifice … is never easy, Davos. Or it is no true sacrifice." - Stannis Baratheon