there are PLENTY of very, very, very unhealthy--even dangerous--people who enjoy strings of relationships

Of course. They are in relationships despite being unhealthy, not because of it, for the record.

There are also plenty of fat people in relationships with skinny people. But usually people pick people similar to them. More skinny people are going to be attracted to skinny people, although of course there are exceptions.

And there are very many emotionally healthy people with gifted minds and emotional IQ's who remain single, even if they're valued otherwise by their communities.

Definitely, and I would never claim this not to be the case.

the medical studies show that our social experiences, starting with parenting, measurably and significantly affect the likelihood of both of these. That's not necessarily an "excuse." It's turning out to be a biomedical fact.

Absolutely. It's not an excuse at all. It's an explanation. Those experiences (or lack) create issues with relationships later in life.

All of what you said is true and I don't disagree at all. I still believe that OP will have a better chance of finding and keeping a relationship if he works on his issues. And even if it doesn't result in a relationship, OP (and frankly 100% of the people on this sub) could benefit from attempting to become more emotionally healthy, especially because a life of isolation just pushes you farther and farther away.