I've made similar comments to people both in person and on TA. To me, it doesnt mean "youre going to have a bad vacation if you only have 3 days to spend in NYC." If 3 days is the most time off you can take, then go to NYC and have a blast.

To me, it means more of "if you're going to America for a week, i'd recommend not trying to visit NYC, Niagara Falls, DC, Miami and Vegas." It could be done, sure. But perhaps you'd have a better trip if you spent 4 nights in NYC and 3 in Miami. Of course, some people would prefer to just 'check a box that they've been to destination X' and thats their choice.

I've also suggested to friends in the Northeast USA "if you only have 3-4 days to travel, maybe Argentina/Europe/Hawaii isnt the best idea." Perhaps you'd be better off not spending 20 of your 80 hours of vacation in transit. But if you really want to get to a given destination and this is your only chance, go for it. (similarly if you're in London and only have 72 hours, maybe you'd be better off going to Spain than to New York)

Finally, i've commented on TA when people look to spend 3-4 nights at Niagara Falls. Sure, there are things to keep you busy there, but if you have a limited amount of time on vacation, i think 1 night is more than enough.

End of the day, these are people posting to TA asking for help. So i'm not sure why the OP is getting so upset when the feedback you're getting isn't exactly what you're hoping for. It's your travel, it's your life, do what makes you happy.