Your point about incentives is exactly the structural problem here. I've been a consultant years ago and on a human level we loved projects that ran well. You feel good about yourself and your team for helping the client quickly and efficiently.

However, zooming out, it's the incentive system that's completely broken: there is no skin in the game. Consulting firms are too detached from the consequences of their advice. Nassim Nicholas Taleb wrote a nice book about this phenomenon: https://en.wikipedia.org/wiki/Skin_in_the_Game_(book)