I am far from a solitary person and I don't think writing necessarily needs to be a solitary habit at all. Nor do lone-wolf writers have any advantage over more sociable folks in the trade.
You can be solitary and still write, but you do not have to be lonely to write. I imagine your productivity in writing would eventually suffer if you sacrificed human contact you wanted.
What do you care about? Look at your writing; chances are you've got a topic in there you're passionate about. Do something in the real world that relates to that, and you
will meet people who like you. For example, I help out with various forms of political action. You sure as hell don't have to do that- if, say, you find that you really value entertainment, then entertain! Take up improv or, if you don't feel adventurous enough for that, cultivate your fun-based conversational skills.
I'm very sociable, very open about the fact that I like people, and as a result, though I get lonely very easily, I have rarely ever been lonely. I make a concerted effort to avoid people who are particularly selfish, and tend to keep away from solitary-by-choice people to a degree (it would probably be cruel of me not to
).
I take a notebook with me everywhere and perhaps you could try that. I like to have my hands free, so it goes in a my pants pocket. My notebooks have been handled, borrowed, returned, written in, read from, and inquired about by every kind of person in this city and I consider my writing to be enriched for it.