This is a pretty common problem, but it comes with the territory. As we used to say when I was mostly in the mobile space: "everyone has the next great app idea."

Hey, I take offense to this comment ;) Just kidding of course being rejected is a great motivator for some. Having devs reject ideas inspired me to learn to program, and realize that there are a ton of bad ideas, and only a few deserve the time it takes to build.

Just to be clear, I wasn't talking about co-founders with unrealistic/ridiculous ideas. I was mostly concerned about co-founders who only bring the idea to the table.

As a technical person, I'm mostly interested in finding a co-founder who would have solid domain knowledge, or have experience pitching to VCs, or any other skill that can actually contribute to the execution of the idea.

Ideas are cheap, everyone has ideas, a good co-founder will help with the execution and there is plenty to do apart from the technical aspect.

I agree with this. And from a co-founder side show me someone that has actually talked to a few potential customers and people are willing to pay for the service. (B2B or Enterprise type market) Now let's talk about an MVP.

And for whoever is looking for someone like that: don't fall for promises like: I have a great network, or I'm a great salesman. There are a lot of predators and leeches out there.