How to respond to a project manager?

Question

Project management

There is a large project, everyone in the team understands its importance both for us and for the client.

Work on the project is moving very slowly, so there are pitfalls during work.
At planning meetings, everyone reports on who is doing what and what has already been done. But there is one section in the project - it "goes" slowly.

We argue to the manager why this is happening, in response we hear the following:
At a construction site, you can load a "wheelbarrow" with gravel and carry it from one place to another, can you say that a person does not work? He carries, does something, but there is no result.

How can he respond to such an argument, and so that he understands that the team is not sitting around, but working?

Answer 1

According to the description, it looks like unaccounted for complexity, the task seems simple, but in fact it is difficult, therefore it takes a long time. As you have already written above, you need to decompose it, break it into subtasks lasting no more than a couple of hours.