The days are long gone where you happily wondered around old rambling stores for an hour or two, just randomly looking for clothes to buy. The old buildings are a pain in the neck with multiple floors, nooks & crannies, random side rooms, basements, etc.
These days, we're in a hurry, we want to be in and out quickly, we want easy navigation to go straight to the stuff we're looking for.
Debenhams is just a nightmare - if you just want a pair of jeans, you have to go to several different areas to see what each "brand" is offering. That means half an hour of trudging around, room to room, floor to floor, just for a pair of sodding jeans.
The only store of theirs that I've actually liked and bought a few things was on an out of town retail park (can't remember where), which was just two huge floors, nicely laid out, easy to walk around, easy to see the brands from each other etc. It was heaving, compared with my usual city centre store which is usually very sparse.