I (and my brother) have stayed at Mornington for more than a decade a couple times a year and it has been fine with focus on location, pricing and decent standards.
In my view the latter has now changed. The standard of the rooms and the breakfast is no longer competitive.
The room (facing the street) was “worn” ( my bedside table fell off the wall just by putting a glass on top), there were no mirror in the room/hallway, the Windows’s are old and not very isolating meaning Friday/Saturday partying outside woke us up and the state of the bathroom, including terrible lighting, is now substandard.
Breakfast was fine but very chaotic due to poor organisation. Looks like this property needs a full renovation and we will stay at other hotels on our regular visits to Stockholm.