The approach today involves handcrafting a large code base and tightly mixing the logic needed by the application platform with the business logic. The domain logic gets entangled and obscured by the platform logic.

Eventually, the code base grows to a very large size and slowly entropies as it gets maintained and enhanced by many developers. At some point developers become afraid to make changes as it becomes next to impossible to understand how it all works. Clever developers leave and avoid working on such systems leaving only those who really value job security and technical obsolescence.

The business is either forced to repeat the process through an expensive rewrite of the system or accept the constraints on their business and slowly work around it. This is the state you will find most enterprises in.