We primarily want to use DDD in the areas that are most important to the business. You don’t invest in what can be easily replaced. You invest in the nontrivial, the more complex stuff, the most valuable and important stuff that promises to return the greatest dividends. That’s why we call such a model a Core Domain (2). It is these, and in second priority the significant Supporting Subdomains (2), that deserve and get the biggest investment. Rightly, then, we need to grasp what complex means.
Use DDD to Simplify, Not to Complicate
Use DDD to model a complex domain in the simplest possible way. Never use DDD to make your solution more complex.
What qualifies as complex will differ from business ...