Add to the mix, turkeys and Christmas
As always, great points.
If I could add one further: The users in these situations are not going to suggest processes that result in them losing their jobs. Consequently, there's little by way of incentive to be more efficient with the new system.
In any change, I've tried to group people up into:
People who want the change
People who will benefit from the change
People who will be disadvantaged by the change
You need a different means of engagement for each category and be clear about which groups & individuals are in each. Conflate them and disaster will happen. Malicious obedience is very difficult to undo once it's set in.
Most project set out with the assumption that everyone has the same intent in mind. This is rarely the case for the above reasons. As a consequence, requirements are captured in a way that assumes they all have equal validity, which of course they can't.
On top of this, there's the challenge of those within an organisation who are experts at what they do as they've done it for years. Sure they have hugely valuable insight into how it has been done. But that's not the point of the new system. Taking 10 your old processes and welding them into a brand new system is usually a bad idea. They cost a small fortune to customise into the last system and will cost a large fortune to weld into the new one. What's needed is a step back with someone who knows what that process looks like at it's most efficient, present that and then see how far from 'good' the clients wants to be, based on specific business / vertical needs.
As someone further up stated, this is not a path that's easy for a consultant to follow as you're instantly up against the established knowledge and as such you often have to back down to keep your job.