Big cities let people find their community because therefore a lot of different ones to try.
You should read the horror stories from so many of those NYC co-ops. Some would make even the most jackbooted HOA presidents blush.
I don't really think this is unique to cities of some specific size. I definitely agree that it's going to be harder to find a perfect fit in a smaller town. But it's also harder to meet people at all in an anonymous metropolis where you have to work 75 hours a week just to make rent.
If you take away anything from what I have written, it's that I think this dichotomy is bad. We need a compromise. The lowrise old-world city is what worked for our species for at least 5 millenia -- it's only in the past couple of decades we decided to rethink it and force a schism between the fake rural aesthetic of the suburbs and the productive, efficient downtown -- and in so doing we destroyed both city life (by making it ungodly expensive thanks to the immense financial drain the suburbs and lack of continuing infill development represent) and the peaceful countryside life (by putting to death small towns in favor of the interstate highway big box store commercial strip). The only lifestyle that has weathered and still works pretty well in this day and age is the homesteader life, and to say that way of living is not for everyone is definitely an understatement.