I think you need to focus on your strengths and your personal interests. Many startups etc are people trying to fix things they lack in their lives or they can do better.
How does this work if you’re a “niche person in general”. Hell I don’t even solve half the problems I have because 1) They typically are more of a minor annoyance than a major problem and 2) When it comes to solving them, I quickly realize the solution is significantly more complex than I originally envisioned and the time and resources required to solve it aren’t generally worth it.
I feel like you are being a bit too hard on yourself. What do you enjoy about solving problems? doesn't matter how minor.
You mentioned you don't even solve half the problems meaning that you manage to solve the other half. What is the difference between the ones you solved and the ones you didn't?