The launch gets the applause, but the system lives for years afterward in the hands of a team that did not build it. Designing for those people, the inheritors, is what separates a demo from a product.
The launch is the easy part
Any capable team can make something impressive on demo day. The hard part starts the morning after, when a different person has to change it under real constraints without the original context in their head.
If every change requires the builder in the room, the system is not finished, it is fragile.
Build the seams to be found
Designing for ownership means making the seams legible: clear boundaries, obvious extension points, and the reasoning behind decisions written down where the next person will look.
The measure of success is simple, can the inheriting team make a confident change on their second week? If yes, the system was built for them, not just for the launch.
