“I personally think that the weather here is dreadfully boring,”
Ironically, you just made the argument as to why SD has the best weather in the country. If you live in a place where you don’t have to think about the weather then you are free to enjoy your outdoor activities year round. So many people living in SD take this for granted and when they go to other climates they are literally shocked that they only have a few months out of the year to enjoy the outdoors.
“Similar arguments could be made about the outer banks, or the coast of Maine, or NYC”
I cannot believe that you mention Maine and NYC in the same sentence as SD but I can somewhat see the comparison to the outer banks.
The outer banks is one of the most beautiful places on the east coast and would be a great retirement choice although I would prefer say a Kure Beach near Wilmington because it is closer to a major city (Raleigh). Prices have come down on the NC coast but it is still expensive and jobs are scarce. If you don’t need to work, love the beach, and don’t mind the occasional hurricane then these are great retirement choices. Yes it is pretty humid but if you get close to the water the breeze makes it comfortable. Pretty much a paradise if you can find something to do or have enough $$$ to retire and don’t mind being 3+ hours from a major city and airport.