Depends what else is going on at an airport in addition to scheduled flights. I think there is a tendency to discuss an airport's viability simply by looking at the number of scheduled routes and the passenger numbers they attract. This is a bit like discussing the viability of a Tesco's by just looking at its veggie department. That said, it could very well be that Dundee is almost only selling veggies if there is little/none GA or business charter activity, no MRO facility, no FBO, no law enforcement/medical related operations, no freight or military flying etc. (which, IIRC, is more or less all the case...)