Why do most gov websites look like they were created by someone's 10 year old nephew yet cost millions to make?
— Steve Dekorte (@stevedekorte) December 29, 2011
I think this aptly summarizes the results of a waterfall methodology.
- You wrote a lot of requirements, not fully understanding the actors or their use cases.
- Your vendor implemented those requirements because they were contractual obligations not because they created value for the actors.