The ships I have sailed that looked the most "shabby" were ships that were going to be taken out of the fleet.
Ocean Princess before it was transferred to P&O (since then it's been transferred back) had railings desperately in need of varnish. Carpet that was stained and had some tears and the exterior was in need of a paint job. It was interesting because the ships was less than four years old when I sailed her.
The other was the Celebrity Galaxy before she went to TIU and was renamed "Mein Schiff". Even in a Royal Suite the carpets were worn and the pool deck looked worn and in need of paint. Also the seats in the theater were worn and number of them broken.
Otherwise most ships are kept quite nice.