How can I finish an unfinished project?
The short answer
Start by deciding whether the project still serves a purpose. If it does, define the smallest complete version that serves that purpose, not the largest version you can imagine.
Published
Name what done means
Who needs the result, what will they use it for, and what must it include? Separate requirements from improvements you would like to add. Do not remove safety, accuracy, or agreed obligations to make the task smaller.
List the remaining steps and the decision that is holding them up. A project may look unfinished because no one has agreed who can approve it.
Keep a separate list for later improvements, so a new idea does not automatically become another requirement for the version you are finishing.
An imagined example
Imagine a guide keeps growing because you keep adding chapters. If the reader needs help completing one task, a shorter guide with that task fully explained may be enough. The extra chapters could become a separate decision.
Make the final agreement
Choose what you will deliver, who will review it, and a realistic date. Ask for necessary feedback before the final handover, rather than waiting until you have made every possible improvement.
Once delivered, record what remains outside this version. Closing a project does not forbid future improvements. If the purpose no longer matters, a clear decision to stop may be more useful than keeping the project permanently half open.