Probably cities can be Mustachian, but NYC apartments tend to not have decent kitchens, and cooking is such a big part of Mustachianism that I'm not sure how it could work.
I have found this true only in limited areas of NYC. I have lived in 7 or 8 different places here, and there was a full kitchen in all of them. The smallest was in the UWS, but it was still usable. (For one person at a time... That was an outlier, though..) The biggest was a beautiful, newly renovated open concept with granite counters and room for a dining table.
Tiny kitchens can still be made to work. Smitten Kitchen does all her cooking and photography in a small NYC kitchen. She has some photos here:
https://smittenkitchen.com/about/Or think about the nomads traveling in an RV with nary but a hot plate to feed them?
Regarding general size, I live in sub 800 sq ft and think it's too big, but I also don't have kids or pets.