I think that the MD-80 was simply not well-suited for the routes they served. This route-structure needs aircraft like the ATR 72, no mainline jets – regardless of the type. Just look at Insel Air/Insel Air Aruba. They are using MD-80s in a different way and their route-structure is much better suited for an aircraft this size.
BTW Airlines like Insel Air use a very simple marketing-tool: they claim that they are operating as stated in their schedules. This might sound very strange but look at LIAT: many complain that LIAT is not flying as stated in their schedule, aircraft depart too early or too late. LIAT not only stands for “Leeward Islands Air Transport” but “Leave Island Any Time” oder “Luggage In Any Town”. Companies like Insel Air/Insel Air Aruba, DAE and even REDjet saw this as a big advantage: to fly as scheduled and without leaving baggage behind.

Strangely REDjet operated two MD-82s while the third MD-80 (an MD-83 with new hushkits) apparently never entered service. REDjet applied for essential landing-rights for flights into the USA (as a “main market”) but the airline never received permission to enter this important market. A route from Bridgetown to Miami would have been much better suited for an MD-80 btw..

Bye!