Yes, the decor is bad, but that is no excuse.
I have noticed that IAD has more than its share of morale problems amongst the staff.
I have had more bad experiences there and although I smile, take an interest in people, and try hard, I have had some real run-ins with some of their folks. Never got any satisfaction from management on that, either. Some of the gate agents are especially bad.
But of course, your mileage will vary when we are talking about interactions and chemistry between people.
I have heard better things about the International First Class Lounge, but have never visited there myself.