I mean I am developing custom business applications, the customer and also the in-house developers have the knowledge. But sure, if you are trying to build a pr

I mean I am developing custom business applications, the customer and also the in-house developers have the knowledge. But sure, if you are trying to build a product you want to sell, then you or at least your team or company should certainly have deep domain knowledge. But this seems also really self-evident, how would you even build a product for something you do not understand? And whoever had ever to become familiar with a new domain will probably know this - from the outside and with no or limited knowledge things look often not very complicated, but once you dig into it, even the simplest looking domain has very deep rabbit holes everywhere.