Aberdeen doesn’t have the long term market for Ryanair at 189 seats, they have to juggle and run seasonal on destinations to keep things fresh and in demand.
As 73max and A321neo becomes the norm the ability to fill becomes more difficult @200+ and the aircraft efficiency cannot compensate enough, you then lose the carrier.
The saving for Aberdeen may be one or all the following:
C series / A220 = a right size very efficient aircraft that makes money on lengthy sectors at 125+ seats.
A Mid East carrier (Preferably Etihad or Qatar) coming in with A321LR.
US carrier (Jet Blue) to JFK with A321LR and connections into their network.
Ignoring Brexit and any freedom to travel issues that may arise.
Issue for the long term. In addition the O&G tied market is Aberdeen’s short runway, to me it’s a scandal that the full 300 yards wasn’t laid (it should have been 500) but the owners at the time - Heathrow Holdings - were never due conflict of interest going to let anybody fly any distance direct from Aberdeen other than to Tenerife.