Thank you for sharing, it's good to get outside perspectives on issues like this. I'll share a bit about myself as well, so you can get a better idea of where I'm coming from.
I don't consider myself on par with most of the stuff I see here either. I consider myself above average intelligence, but nothing special. I'm not particularly creative, but I love being part of the creative process with other people. If there's something I pride myself on, it's my ability to facilitate meaningful and effective conversation. I'm not very confident in myself; I think my above average intelligence lead me into contact with enough people who are simply smarter and work harder than me that I don't have any false notions of grandeur.
I get how work can provide you with a sense of purpose, I really do. One of the things I would do, assuming I didn't have to work, is volunteer for a non-profit that tackles an issue/issues I feel are important (like clean water for everyone). My personal projects would basically be two lifelong ones and whatever else caught my fancy. The first would be a music recommendation system that works differently from most others I've seen (any I've seen? copyright Jeff Holland, 2016): it would let you find music in genres you normally don't or have never listened to. The idea is, you can say "I like Queens of the Stone Age. What rap artists do QotSA fans like?" and it would suggest artists (and songs) accordingly. The great thing is, the sky is the limit when it comes to refining and expanding something like that, the challenges are technical and algorithmic. The second project would be a traditional roguelike with a different progression model for characters and story than is usual, with a technical focus on being truly cross-platform and providing a means of playing games via TLS on a central server (a la DCSS).
I know that was probably way more information than you wanted, but I wanted to give you some background on me. I'm not amazing or confident, but I do have a few things I'm passionate about. If either one of my personal projects was successful I would be incredibly happy. It doesn't even have to make me money if it makes enough to be self sustaining and the users find it worthwhile. All to say, I understand the feeling you can get from producing something valuable for others, and even enjoy it. I made a conscious decision when I was young(er) to disconnect that from my sense of self-worth, and it's now ingrained in me.
Essentially, my hobbies take the place of where the need to feel wanted would be. There's so much out there to enjoy that I don't mind if I'm not necessary (are any of us, really?); I can share the things I love and appreciate with others.