Building a solo business is impossible?

I, like many engineers, dream about turning my love to programming into a side business. Nothing crazy, but enough to replace an average SWE income. And I, like many engineers, fell into the "build, and they will come" trap.I tried to build, calibrate, engage in SEO, talk to customers, but I can't seem to find traction. On one hand, people say that you need to build to solve a problem. You find a problem in a niche, say accounting for plumbers, and build for that, then you just go and market to these people. On the other hand, I see people who advocate for "I just built something that I needed, and it got traction". There are multiple examples for both camps, but the problem is that they contradict each other.This leads me to believe that most people either get lucky and then apply a framework in retrospect to justify their luck, or they simply don't tell the whole truth.I want to escape a salaried coder job, more so with the "push" of vibe coding across the board. But I have no idea how to approach a business. I refuse to believe that everyone who succeeded with a side project and replaced their job - is a liar, but maybe the truth is that it does not take 7 months, but 7 years?Anyone got something helpful to share in that regard?