Totally empathize with you and I've been there. At some point, it does make sense to exit amicably in these situations. My experience has been that the non-technical founder will see things as they truly are, eventually.

At that point, you can re-establish another engagement where things are budgeted for a balance of speed and longevity.

To be fair, there is a purpose for Technical Debt and for cutting corners, esp for MVPs or demos. But it has to be a balance and the cost of the debt carry has to be appreciated.