I think you are very insightful and have hit the nail on the head. You are lonely, and loneliness - especially chronic loneliness - easily leads to depression.

I would also strongly agree that being intelligent has its downside. A lot of what intelligence makes you aware of are aspects of reality that are not happy. I read of a study that was done on the relationship between being realistic and being depressed. Initially, the reserchers were testing the hypothesis that depressed people have an unrealistically grim view of life. Well, that's not what was born out by the data they collected. They rated all the subjects of the study for mood, on a spectrum from depressed to optimistic. Additionally, they, in some manner or other, rated the study subjects for their tendency toward realistic thinking. They found a correlation. Truly realistic people are unlikely to fall into the category of being very optimistic in their outlook. Depressed people, by and large, rated higher in realistic thinking than optimistic people. One of the conclusions was that, if you want to be an optimist, it really helps to not be a highly realistic thinker. So there's some validation for you.

Getting back to the socialization issue. In life, there is a price for everything. That's an old saying, and, the longer I live, the more I find it to be true. Trying to put yourself out there socially does involve risk. You risk being bored by people and you risk being hurt. Of course, there is a price for sticking to a socially avoidant lifestyle. The price is loneliness, and you know how that feels.

I guess it boils down to which price you want to pay. You can't change the fact that, as a human being, you need human contact. We are social animals, and we wither inside without satisfying interaction. There is a catch. You can't get some satisfying interaction without putting up with some non-satisfying interaction. The non-satisfying interaction ranges from mildly annoying to dreadfully hurtful. Spend enough time around enough humans and you will experience that whole range. That's the price of full social participation. However, if you stick with it, you will mature emotionally. That means you will develop some armor over your sensitive soul. You will become more resilient in the face of interpersonal challenge. You will grow.

Seeing as how you don't like where you are at because isolation is resulting in depression, I would recommend you approach life differently from how you have been doing.

At times people will bore the p!$$ out of you. But, over time, you can learn how to shorten those encounters. Now and then you will be hurt, but you will discover that an occasional case of hurt feelings isn't the end of the world and won't kill you. Sometimes, it helps to just say, under your breathe: "Yeah, and screw you too." You can learn that you don't have to react to everything.

You can, with effort, change your vulnerability. You can't change the fact that you are hunan and need social interaction and a chance to find love and friendship. You are hard-wired to need warmth and affection. You can't change that.