It is essential to separate project success from product success.
For a project to be successful, it needs to meet the success factors set out for the project. The success factors must be measurable and within the control of the project. If the success factors are not in control of the project they should not be used as success factors. If they were it would mean the project could do everything right and still be considered a failure as a project.
What a project creates is a product. There is always the chance that a successful project has a product that doesn’t realize value. It is similar to a poker hand, you may make the right decision but still lose the hand.
Part of starting a project is determining the chance of the resulting product producing value. If there is a low chance of realizing the value even when the project is successful is a reason not to proceed with the project.
Having the two viewpoints allows better decisions and better plans to be made.