Sure it is important, so you and project team will try to avoid the issues occures on this project in the upcoming projects.
Not all leasons learned have negative impact some of these have positive impact we can call oppertunities, we can increase number of oppertunities in the upcoming projects.1. Adding significant requirements while project execution process, this one has negative impact.2. Re-sell your ideas and the benifits if this project, change management will become easier. This has a positive impact.
And so on