Ok, but technical co-founders in tech startups are also less valuable than they think (as this blog post shows).
In reality there are four critical skillsets (outside fundraising) for a new tech venture: Operations, Sales, Product, and Engineering.
I've seen plenty of startups with a heavy focus on product and engineering flail about because they suck at operations, product, or sales. The harsh truth is your CEO better be excellent at one of Operations, Sales, or Product, and your CTO better be excellent at one of Sales, Product, or Engineering. And if your CEO isn't competent at operations, you're going to need someone who is. Dealing with HR, accountants, investor relations, lawyers, contracts, HR, and all that stuff is a big job that's hard to completely outsource.
Overall, if your founding team isn't at least competent in all four areas, you've got a gap that will be difficult to fill unless one of the founding team is willing to step up and learn that area fast. Sales (or marketing, for consumer apps) might be the exception, because in my experience everyone on the founding team will wind up needing to learn it early on.