This game is very reminiscent of Plateup to me, with a difficulty curve to match.
I experienced two layouts, the one track layout and the two track layout. I was able to load both trucks with the one track layout, but massively struggled with the two track layout. Walking time was everything in this game because the tasks were either quick or set-and-forget. The two track layout was awful because you had to hope you were on the side that matched the extra task a box demanded, or the walk might not even be worth the box.
There is a bug in which the taping minigame would stay up after taking the box off the taping desk. It goes away the next time you tape a box.
While the work is strong, there are missing pieces to a complete experience. That said, you've done well to capture the vision that you were going for (your time at FedEx).