Before launch, most decisions are based on research, experience and assumptions. After launch, the business starts receiving evidence from real customers and real workflows.
That evidence may show that a page needs a clearer answer, a form asks too much, a campaign attracts the wrong question or an automation needs a better exception route. None of those observations automatically mean the project failed. They mean the business now has something concrete to improve.
Build review points into the work. Good delivery creates a useful starting system and a way to learn from it, rather than pretending every decision becomes permanent the moment it goes live.