Imagine the application you're currently working on. Imagine your users were happy with a primitive text based UI in a console, and imagine persistence was not an issue because you have an obscene amount of RAM (a billion terrabyte) and your server never crashes (so no DBMS needed).
Would there be any complexity left to deal with in your software? If the answer is no, you're lucky (in a way). If the answer to this highly hypothetical question is still yes, then domain driven design (DDD) might be the thing for you.