I'd point out though that it's an entirely different market today than to 2003/2004. The longer runway argument wasn't valid then, but now with the 737 Max-10 and A321neo making it possible to operate medium haul routes with 200+ passengers, it's quite possible that some interesting connections could be opened up. Of course, it won't work for genuinely long haul, but I wouldn't rule out an airline like Easyjet trying things like Marsa Alam where they could sell a large amount of seats to tour operators in winter.
The A321neo and Max-10 on longer sectors probably wouldn't be able to use LBA if they were fully loaded in a typical low cost or charter configuration.
The 757 would have been restricted in some way as it would have needed a runway of between 2100-2400m. I can't imagine how the 747 or A300 would have done it without some major restrictions, unless these were short haul flights - a long haul flight would need a lot more runway than LBA has.
Tenerife is closer, but again, what are Jet2 using on those flights? If we're talking about Dalaman, the A321neo would be *very* close (if not over it) to the limits of LBA in summer if we're assuming a fully loaded 232 seat plane. They could do it with some seat restrictions, but there's no denying that LBA needs a 200-300m runway extension.
Well, don't forget that some other places are now starting to fight for tourism, such as Baku. Then, as Europe becomes more and more expensive for tourism, people are looking for cheaper destinations, so you've also got to consider places like Batumi as being commercially viable in time. Of course, LBA is perfect for most missions, but there's certainly a niche in catering to medium haul cheap flights where the goal is simply to pack people in for 5 hours or so.
I don't think DSA is viable by itself, but I also don't think it's a lame duck if they're able to attract an airline willing to put on a reasonable amount of flights.