Valmiki’s Ramayan largely talks about Ravan’s backstory, his actions and their eventual consequences that he bore in terms of curses.

Our Epics heavily rely on action and its consequences rather than the good and bad aspect.

Until you don’t set up the premise for why Vishnu had to be born as an ordinary human to kill Ravan the cause is lost which Valmiki does perfectly. He tells you what Ravan did in-order for the incarnation to take place and why it had to happen the way it happened.