Those who denigrate aerospace projects for being over budget and over schedule are either naive or disingenous.
The unfortunate reality is aerospace companies are strongly motivated by the Federal Gov't proposal selection process to bid too low and too fast for high-risk projects like JWST. While not truely "lowest cost" bidder selection, it's understood that a winning bid will be in a certain range, regardless of whether its realistic. And the schedule proposals must also target certain bogies to have a chance of winning, regardless of winning.
And so companies bid low and fast to meet the proposal expectations and requirements, knowing that they'll make it up in cost-plus overruns as the Program proceeds.
And those running the programs know this too.
And ultimately, each project such as JWST is a one-of-a-kind endeavor. New technologies, new manufacturing methods, new test techniques are invented during the course of the project. It's difficult to predict the budget and schedule for doing something never done before; much less keeping to an optimistic budget driven by political needs more than the technical.
To those on JWST, they are doing incredible work, putting in long hours, and coming up with creative solutions to very challenging problems. And everyone of them wants to see JWST succeed.