I'm also convinced that we exit the plane in the worst way possible. We basically do it row-by-row: as the people in front of them leave, people in a row get up, get their bags, start walking down the line, and this cascades up the plane. The problem is that there is very little parallelism: while people in the next row to leave are getting their bags, no one is exiting the plane. This is similar to a stall in a proc…
However, you can't start boarding until a certain point and from there until the plane leaves the gate, a lot of resources are locked.