Maybe some abstract philosophy from the 19th century isn't the reason that, all of a sudden, people are more lonely and depressed.
The less I engage with America's consumerist mass media society, the less lonely I feel. I felt more lonely when I watched TV, listened to the news, read the paper, scrolled through social media. Everywhere there was a reminder of the life I'm not living, stuff I don't have, other people's lives I'm not a part of, and of course, impending doom.
I disconnected from all of that and moved to the woods. 2 years later, I've never felt less lonely. I am so constantly busy with gardening, composting, cooking, chores, repairs, building things, fishing, hiking, paddling, that I barely have time to watch a show or check my phone. I feel no existential angst, no FOMO. It never crosses my mind that there's something I'm missing out on. I'm busier than I've ever been.
Where others might think about politics, buying a new car, which restaurant to go out to, trying to cancel their gym membership, trying to find someone to go on a date with, or who's party they weren't invited to, my biggest concern is the weather. When it's going to rain, what temperature it is, how much sun there is. I guess mice is another big one; trying to figure out how they're getting into the heating ducts, or how to keep them out of my car. And snails; they're devouring my seedlings. So, weather and pests.
I don't really know what loneliness is now. I can always open a window and listen to the birds, watch them go about their lives. I can even engage with them, feeing them, building them a home, calling them. I can dig up my garden bed to plant something new and see all the activity going on underneath. I can check out the plants and make sure they're healthy. Life is everywhere, and I can engage with all of it, any time.
If I had to engage with humanity all the time, yeah, I'd probably get lonely and depressed. But like those who moved out into the wildnerness of the Old West, I have the luxury of not having to be constantly reminded of humanity. "out of sight, out of mind" is true enlightenment.