Well, in my experience most developers who are working at a job don't set the bar quite so high. In fact, if they can make about 1/3 to 1/2 of their salary
without having to work at a job, that's already considered a victory, although of course people don't stop there.
And that's kind of the point... once you've built a business that successfully and reliably provides 1/2 your previous salary without working for someone else (i.e. building a product or productised service, not a plain service/freelancing), you can probably increase that to 1x, 2x, etc... whereas before, there's a hard glass ceiling above you.
Obviously that equation is less appealing if you're already well off financially - hence your distate of the business idea you came up with.
Which is fine - one of my friends who applies this method has in fact done exactly the same thing - built a small business, figured out how it would be profitable, then decided that it wasn't the kind of business he cared about building, and so shut it down and looked at another idea.
Product-market fit and idea-founder fit are equally important - at least when you have the room/comfort to make those decisions!