All these factors may have played a role in why your shoes do not feel good. I must say that the first few days, I thought mine felt "hard" on the bottoms of my feet. But they were immediately more comfortable than the custom orthotics ($300) I bought and could not wear in my shoes. Now although there is no cushion to these shoes they fit like a glove even when I get a new pair. Although I now have 3 pairs, and I think1 of them is not quite equal in comfort to the other 2.
One other suggestion I can make is that you do need to somewhat adjust you walking style while wearing these shoes. I tend to move my leg forward from the knee in a smooth almost sliding manner (which allows me to walk without bending the arch of my foot). It means walking slower that usual - and I used to really strut! When you wear these loosely if you don't walk right you step out of the shoes or trip and if you do it correctly, you get "shin-splints" in fronts of your lower legs for about 7-10 days when first starting to wear them. The clerk explained all this to me - she was very helpful and knew her shoes... anyway I did get the sore shins and the rest is history. I'm doing really well now and plan to keep wearing them. Hope this is helpful to you and others who'd like to try the birks. Diane R.