Domain model consistency

When it comes to modeling, we often hear that data models need to be at the center of any system. If you want a good system, you need a good data model. I have heard that saying countless times in my career as a software engineer. One of my colleagues once said this, and then added: "I participated in a large project where we started with defining the data model, and, after eighteen months, the project was shut down because the model wasn't complete." Strangely, these two statements created no causal relationship for him, since the first statement was an axiom, and the project failure seemed to be caused by numerous reasons, but not by the fact that designing a single data model for complex systems is always a death march—many tables, directly and indirectly, connected to one another by foreign keys, an endless push for the third...