Being alone in the city, "alone in the crowd", feels just as lonely if not more so for me than walking alone in the forest. The latter I expect to be alone, but in the former, I'm surrounded by people but with no connection. It's a strange feeling.
There’s a new lot coined word “sonder” that describes being alone in the city and observing others and wondering about their inner lives. As a writer this fills me with warmth rather than loneliness.