Understanding 'Insular' in Urban Context

In the following passage, the author reflects on the complexities of modern urban life:

'The city teems with people, yet one can easily feel insular, surrounded by the vastness yet distant from genuine connections. Those who navigate these crowded streets often do so in a hurried manner, prioritizing productivity over intimacy. Ironically, despite the overwhelming presence of others, loneliness becomes a pervasive undercurrent, illustrating the paradox of urban existence.'

In this context, what does the word 'insular' most nearly mean?