I'm currently building a SaaS with my business partner. I'm the "tech guy" while he has decades of industry experience with the industry that our SaaS is targeting.

What I found building this is there is a giant subset of preferences, problems, and other minor details that aren't written down anywhere, they are just kept in the minds of the people in that industry.

The reason it's not written down is to those people, these things seem obvious. And these things are both extremely important but also very subtle.

We use AI heavily in designing our application but there's always a testing pass where my partner goes over some changes and calls out subtle things of how "things work in practice". These things aren't in any manuals, they are seldom even written down and thus AI systems are completely oblivious to these details.

Now you could build a system that skips some of these subtleties and still gets the job done but what you will find is potential customers will always return to their existing system that takes these into account.

Now one day we might get an AI system that detects these subtleties but in order to do that you would need a load of training data around those things. But how do you even get that training data if all of it is held inside the minds of the people working in that industry?