I'm a self-taught developer with no professional experience, but for over a year I learned everything I needed to know to build a massive web application to fulfill my own need: a collaborative annotation wiki. I poured my freaking heart into it and could never get a single user.
I drew on Jimmy Wales' experiences founding Wikipedia for a lot of inspiration. But got nowhere near the traction he got. As in, I got zero users after nine months since launch. Now it's largely a portfolio piece as I try to search for a real job in tech, by leveraging the 14,000 lines of code in Python/Flask to prove that I know how to develop an app. ( https://anno.wiki is the url if you're curious).
I can only hope that the real reasons I haven't gained traction are that (a) the interface just isn't welcoming enough (I tried too hard to do progressive enhancement with almost no experience in UX) and (b) simply not advertising. After a nine month break I'm getting ready to start re-developing a new front end in React to maybe make it more welcoming to non-techie lit nerds, and then maybe target advertise on Facebook, but I just don't know.
My deepest fear is just that the web is not an interesting place anymore, and Wikipedia just wouldn't get a foothold now, and that's why I can't. I just don't know.