I don't have problems with learning and building the apps, my problem is how to come up with an app idea that people would actually use, and I could monetize it somehow.
But coming up with that idea, executing it correctly and having a whole lot of luck is out of reach for the majority.
I wouldn't underestimate the luck part though even if you do come up with a brilliant well executed idea.
I've acquaintances who spent years trying to commercialise side projects that have eventually come to nothing. A lot of disappointment but I guess you've got to put the hours in and try something to even have a chance.
Personally always thought the idea of something low key with a continuous income stream sounded the most realistic, as others in this thread allude to. But you still need the idea, the execution and the luck.
For me, I got a lot of exposure to these problems in the time I spent working at startups using technology to solve big problems in large industries that aren't conventionally "tech" but this is a long term play; it took me a decade of doing this to start to develop a perspective on where my previous companies, as great of a job as they did, still left certain problems unsolved, problems I would go on to solve at my own company. This isn't a quick solution to your problem but it does work.