I think it's remarkably important to surround yourself with people that are meaningful to you; that to me is different from things in common. Having things in common helps provide a medium for bonding but it's rarely the specific activity that is the focus for bonding, it's the shared experience that is.
There are lots of people that I call friends with whom I have little in-common, but there's a specific experience I've had with them or perhaps one specific thing to bond over that has created a strong connection.
Meaningful conversation is important too but I often find that trying to have a conversation I want to have can be productive. Many people are actually very interested in different ways of thinking or approaching life.
You are completely justified in your solitude. As you said, it works for you. Yet I still believe meaningful connections (and personal growth) are abound without superficiality if you are willing to give it time and effort.
...Sometimes I believe it is the disparity between myself and another that leads to a lasting, meaningful connection more so than the similarity.
Well, I guess I can elaborate a bit. I have a bunch of obscure interests, and most people haven't even heard of them, much less share them or are nearly as interested in them as I am. I used to be ok with that, and would hang out with people who would want to talk about and do things that I have absolutely no interest in, but after a while I realized that I was wasting my time doing that.
I'd rather just spend the time by myself, reading about, learning, or doing things that I was interested in. One thing I take great refuge in is reading old books by or about truly great authors and people, and they're always interested in and talk about exactly the things I am interested in, simply because I choose to read only those books which are about what I'm interested in (or am open to becoming interested in).
From time to time, I've joined clubs or gone to meetups of people who are interested in one of the things that I am interested in, but then it's rare for them to be interested in the other obscure things I'm interested in. And I guess that's where I get too picky for my own good, as there's really little chance of finding people who share all or even a significant fraction of the obscure stuff I'm interested in.
Not that it has to be all about common interests. If I could somehow make a deep connection with someone I could see myself getting interested in some of the things they were interested in, or vice-versa. But that's hard to do if you don't already have something in common to begin with.
As to your point about what's happening behind the scenes of a superficially happy looking group of people, I recognize that it may not (and probably isn't) quite as idyllic as it looks on the surface, and that recognition gives me even less reason to seek companionship with other people. There's often a lot of pain and effort involved, and for me it's just not worth it. It's so much easier and simpler to just stay my own best (and only) friend.