I had a former life as a web contractor, and almost half of the projects I did were from individual or small groups of founders. They were usually non-technical or had no knowledge of the web technologies they required. Even though we were able to create some really strong initial products, the businesses themselves never took off.

I think this was often because as a contractor, I finished version 1.0, and then I went off on the next project. I was available for small fixes and enhancements, but I didn't feel it was my job or my specialty to help them iterate or pivot. Without a technical person fully invested in their work, there was no real evolution to their products or their business.

Eventually I came to the point where I no longer took those kinds of contracts, because I either didn't believe in the model, or else I felt that it would only be worthwhile to contribute as a partner as opposed to a worker for hire.

So I think that technical founders are necessary, whether that involves bringing on someone with the knowledge, or having one or more non-technical founders learn enough to become a technical founder.