> I don't even know if this is something people would want or pay for if I completed it. And then there's the task of marketing/selling it, which is way outside of my skillset.

This is why you're spending years and years spinning your wheels getting nowhere. It's a classic mistake pretty much everyone makes.

Very fundamental rule number one: Only build something AFTER you sell it FIRST.

The only time that rule doesn't apply is if you're doing a hobby project / labor of love and you're okay never making money off it.

EDIT: BTW as far as marketing and selling being outside your skillset, it's outside everyone's skillset at some point far enough back in their careers. i.e. nobody is simply born with it. The point is you develop those skills through pain, trial and error. That, or you find a business partner to handle it for you.