Massive over complication of the issue by spotters re NCL!
You have 2.7 million people to use. That will only allow certain routes / frequencies to be viable [even with RYR].
Yes the propensity to fly in the North East is not quite as high as other more affluent regions but the overriding factor is the population catchment of a remote region. Once that 2.7 million are used on viable routes - that is it. No passengers are coming from anywhere else. Hence New York not quite working.
Not like Bristol in the slightest, which has more than double the population catchment of NCL.
The management of NCL are doing a great job and are maximising what is possible with 2.7 million people.