The department store embodies old lady consumerism.
It's where you go to find mediocre but overpriced products. It's where your mom bought clothes for you that you didn't really like. It's where your mom still shops. The pricing structure is based on making moms feel like they got a good deal on a "sale", but actually everything is just overpriced and you can't get things with the appropriate price unless you play their dumb game. There are stories about department stores stopping this and losing lots of sales because their customers were addicted to it.
They simply failed to change to attract new generations, their buyers couldn't buy for the next generation, so they kept targeting their aging customer base until they were gone and poof, no more department stores.
You probably could do a new generation of department store targeting younger folks, but it would have to be much different. Probably won't happen.
My last department store trip was to buy socks, they didn't have what I wanted, then I paid an outrageous price for average athletic socks because I didn't have the right coupon, store card, flier, whatever. I wanted socks more than I wanted to go through the trouble of buying nicer or cheaper ones on the Internet as I was already there.
Kohls has a deal where they will give you a substantial coupon if you return something from Amazon to the store. Fuck me though, I'm not going to do the obvious scam.
I'd feel less ripped off spending $50 per sock at Hermes.