The root of the problem isn't using or not using COTS.

The root of the problem is the government keep hiring consultants they pay by the hour. They they act surprised when the consultants respond rationally to the incentives.

Or they agree to a fixed price contract where everyone knows the government will pay you more if you say you can't deliver and threaten to go bankrupt. Then they act surprised when the contractors respond rationally to the incentives.

The government needs to break projects down into smaller chunks, to mitigate the losses if a supplier doesn't deliver, you don't pay them, and they go bankrupt. Then they need to establish and enforce an incentive system where suppliers are punished, not rewarded, for failing to get the job done.