I think the difference with stores like The Gap and J. Crew is that the dressing rooms are modernized. They are more public that Macy’s, very well lit and often with locks on the doors and floor-to-ceiling walls. Macy’s, on the other hand, are dimly lit and in the far reaches of the store - ripe for trouble.
But I well understand your discomfort having a young man sitting right outside your door!!
True, there was a lock on the door. But not two feet away the young man sat and talked with the girl he was with the whole time while she opened the door of her room and came out modeling, then went back in and tried on some more.