Have you ever tried to convince someone to join a truly ridiculous idea? You'd be surprised. People aren't that stupid. We are talking about someone joining as a co-founder. Therefore, that person has some basic notion of what a co-founder is, what a startup looks like, etc. We are not talking about finding a random person on the street who'll give you a quote "great idea".

For the best idea in the world, I also challenge you not to find anyone who believes in it.

Now, to be practical rather than extreme, my experience shows me that having co-founders brings a lot of value during the brainstorming phase. Although I like to think of myself as very smart - I could figure out everything on my own, right? Co-founders bring balance. Once in a while, I have a crazy idea that deserves to be killed. But I'm crazy enough that on my own, I might do it. With co-founders, you get very quick reality check.

The secret is to find co-founders who share your vision 90% of the time, and help keep you on the right track the 10% when you are wrong.

If you don't share the vision with your co-founders and can't even agree 50% of the time, then you are correct: it will be a waste of your time, arguing endlessly about trivial stuff.