People who are the source of the problem usually also have the solution.
While a lot of the problems on a project are created by people (bad estimates, feature creep, wrong strategy, poor architecture, lack of communication, poor oversight) these are also problems they can solve on their own.
The reason for the problems isn't always incompetence: there are often constraints invisible to you that get in people's way. Ask them how they would do things differently and then give them the chance to do just that.
This is particuarly true if you are a manager:giving your team room to find creative solutions and fail safely in their implementation will yield astonishing, efficient solutions you would have never thought of.
Remember: you win when the right solution is found, so if they find it you win twice because you didn’t have to do any work. Back off a little and see what happens.