In comparing Copenhagen with Luton it is worth remembering that the Go pier used by Easyjet and other LCCs is a rather bare bones experience compared to the other more comfortable piers at Copenhagen. I suspect additionally that use of the other piers at CPH means higher fees than are charged at Luton. Additionally, the central area (ie shopping mall) of CPH departures can get rather busy at peak times such as 8 pm on Sunday evening; the arrivals / SAS checkin / train station area seems to be overcrowded for large chunks of the day
Copenhagen may be a nice airport overall but it also has its own faults