I also received the same email - as did millions of others.
Having been to 2 of the 3 suggested places (and having a bit of a fetish for islands myself), my first thought was: why in the name of everything holy would anyone want to ruin one of their favorite places by turning it into just another crass, overcrowded, overtouristed, sad wasteland, like (insert the name of a place you arrived at, found it crushingly crowded and filled with the absolute worst kind of thoughtless social-media herds, and wanted to cry or just get outta there ASAP)? See Most Crowded for some examples.
Having worked closely with professional marketing teams at large corporations on product launches, my second thought was: hah, this is just a marketing tool designed to select some of our millions of marketing contacts for even more targeted email solicitations in the future, and has nothing to do with what choices they make; they've already decided where their flights are going to go (large, successful airlines do a LOT of research into any potential new destinations - like everything else today, ruled by metrics, AI and vast sets of data - they're not going to be influenced by what customers say they want because Delta believes their experts know better). Anyone who responds to their question is really just saying: "Please send me more spam!"
The lovely places that Delta claims are now in their gunsights would be a lot better off without a nonstop flight from JFK. If you love one of these places (and I do), either skip the survey, or write-in "Santorini" or "Cancun" if you can.
Edited to add for clarity:
Being inconveniently located and hard to reach is a feature, not a bug.
And it's what keeps amazing places wonderful.
While I love me a nice nonstop to Europe (or any other continent far from home) as much as anyone, once I land there, I am happiest when I eventually arrive someplace more obscure that takes a bit of effort to get to. I've always found this to be true: The quality of your travel experience is inversely proportional to the size of the last aircraft that delivered you there - the smaller the plane that gets you there, the better your experience will be. Even better if after the tiny plane drops you off at some remote airstrip, you then have to take a speedboat for a few more hours to reach your destination. A sketchy dugout canoe and/or wading ashore at the end would be a good sign, too, though not always necessary (and could be an indication you have stretched this axiom to its practical limit). Conversely, nothing kills a place's charm faster than getting lots of long-haul nonstop flights from the world's biggest cities. Well, except for Instagram.