It's not very agile friendly, but emphasizing design early in the process and having some "gate-keeping" protocol such as design review or code review can greatly reduce the chance of something going off the rails like this as it forces everyone to acknowledge what done looks like, as well as what the "missing" pieces will be.

The GateKeeper process isn't something you want to index on too heavily - but you also need a mechanism to counter-balance the possibility of a dev saying "I built a prototype last week that does 95% of the things we want" and 3 months of iteration later identifying that it only did 5%, and that getting the remaining use cases will require a re-write.