They have super traits because they're super human. And fictional, for the most part. The actors on screen are touched up, but they've also put a ridiculous amount of work into looking like that. Often, it's for one or two shots, but they've put in the effort, and got paid for it.
Good job, I say. Man I wish that I had that kind of determination. Money and time too, but they shouldn't take away from the work that the actors do.
If you want to make heroes look more realistic, show things like Black Widow missing shots in training. Show Captain America lifting to failure. Show Batman missing a batarang throw in training.
But show the training. Let the fans know that what the more human heroes have is training, and emphasize that. But remember, it'd be WAY more time looking at training and the X-Men in the Danger Room than it would be them fighting whoever they fight now (I fell off, don't hate me). You'd have 11 issues of hard, monotonous work, and one issue of action. Maybe an annual.