These are all problems you have, not a problem with self improvement.
>The problem is that there are no other people. No socialization.
I learned at a young age to not rely on other people. This can mean that you don't feel a need to improve yourself, which I used to be like. It was easy for me to transition to a state where I'm improving just for myself.
Even if you require other people to be involved, all it requires is some foresight. Your self improvement now improves how others percieve you in the future. This includes hanging out with friends. Everyone I know with a shitty life is miserable to be around. Why would you not want to improve the quality of your life unless if you just don't have foresight?
>The problem is that there are no other people. No socialization.
Why not find a buddy who wants to get fit? Join a book club? Come to communities like this to talk about your struggles?
>If there are other people they are often just an objective (see pua or job networking).
Not all self improvement is this blindly self serving. I just want to maintain my mobility when I get older, learn to take care of myself, and learn.
>It is truly sick. The world is full of people and activities you can do with other people that will make you a lot happier.
>A beer grabbed with a friend will make you feel better than the best workout ever.
Again, this is personal to you.
I am an introvert. Going out with friends is draining and unpleasant, even though I'm as good as anyone at socialization through practice. (They stay in with me so I go out with them, but this is unrelated).
Crossing off something in my planner and knowing that I'm one step closer to the person I want to be is the most rewarding thing for me.
>You can't build great things alone. You can't expect to follow a routine or reach an important goal if you don't consider positive and sincere interactions with other people in it.
My time spent programming alone has been useful in fun group projects. I'm part of a robotics group at my school that I could have never been part of if not for the time I spent in practice. Improving on your own time is necessary for a certain level of rewarding interaction in groups.
>Stop going towards things that make you lonely and reach out other people. You'll see how good it is.
It doesn't make me lonely, I think this is personal to you.
Please don't discourage people from self improvement. I'm glad you're at a place where you're happy, and you're done with self improvement. It's what we all eventually want to reach. That doesn't mean that it's not good for other people with different personalities at different places in their lives.