Cost plus isn’t nearly as common as it used to be.
But you still run into similar issues regardless of the contract structure. Try and build a rail network without anyone in government wanting something changed from the initial design for 20 years.
Yep, because of the incentives. Few people in the government making those choices are depending on the thing actually getting built.
Most are paid to prevent projects with a given defect type from proceeding. They aren't rewarded for the number of projects that succeed without defects. Preventing CYA from running wild is a legitimately hard problem to solve.
But you still run into similar issues regardless of the contract structure. Try and build a rail network without anyone in government wanting something changed from the initial design for 20 years.