I think that's a fair assesment Onion. There's an interesting article on Wikipedia about Sheffield Airport, which basically concludes that they planned it wrong from the very beginning. At just 1,200M the runway is even shorter than Southampton. I'm not sure if any regional jets could be accomodated on a runway that length, but 737 / 320 sized aircraft were certainly a non starter, so the holiday charter and lo-co scheduled market, for which there must be an enormous demand in that area, didn't get a look in. What a waste.
The viability of passenger operations out of Manston has yet to be proven, but as you say, at least the infrastructure is there.