Meh I see what you mean about broodiness not belonging in a Marvel movie, but I don't think they'll take it too far. Iron Man's first half was "grittier" than any other Marvel movie, and that's still my favorite movie by them. Not TDK levels of darkness, but still a little more grounded than most superhero movies. So I'm hoping this'll be a little reminiscent of that.
I did like Avengers but it went so far in the OPPOSITE direction of broodiness that it felt like a consequence-less cartoon at times. I'm glad they're not keeping that tone for the individual movies (or at least this one)