One thing I'll point out is that we get a whole bunch of people-disintegrating scenes running over many minutes when, in actuality, it's all happening mostly simultaneously (exception being Spider-Man's healing factor drawing his out, and if you thought Tony had no emotional reaction to that, I can't help you). In the movie we don't have time for anyone to react beyond initial stunned disbelief. I expect a lot of reactions in Avengers 4.