Bring back Dan-Air... or B-Cal!
Fact is Aberdeen with its one-horse industry is out of favour with airlines, who now struggle to break even on the scheduled business routes. Hence the loss of freqs on some & complete loss of the route on others.
Maybe the answer is a new local start-up using suitable-sized equipment (talking air taxi sized!)... any local entrepreneur out there with a few tens of millions to lose a million? If you can't even fill a J41 then things are grim.
4m pax by 2030 seems a long way away - and I don't think was ever realistic given the volatility of our only main industry.