A team can improve a project without improving the business. If the lesson stays in one person's head, the next project starts from the same position. Operational compounding depends on retaining what worked.
Find the reusable part
After a successful delivery, separate the context from the method. The client, budget and creative direction may be unique. The intake checklist, approval criteria or deployment procedure may be useful again.
A reusable method should make the next job easier without pretending every job is identical. Record the conditions under which it worked and the situations where someone should depart from it.
Give the improvement a home
Put the updated checklist where the next operator will actually use it. A lesson buried in meeting notes has little effect on a handoff. Attach it to the project template, the task definition or the relevant tool.
Make one person responsible for maintaining that reference. Otherwise each team member may create a slightly different version and the apparent standard gradually disappears.
Watch the maintenance cost
Templates, automations and documentation all need upkeep. A large library of outdated processes can be harder to navigate than a small library of reliable ones. Retire instructions when the workflow changes and make the current version obvious.
This is not a claim that every small gain produces exponential business growth. Improvements interact, constraints move and some gains fade. The practical aim is to avoid repeatedly paying for the same lesson.
Review the inheritance
At the next project kickoff, ask what this project receives from the last one. If the answer is nothing, choose one useful lesson and incorporate it. A business becomes more capable when good decisions remain available after the people who made them move on.