Any job will wind up having bottlenecks, these areas with little wiggle room that limit the overall scope of the project. Meanwhile, if you want to make any big picture changes, the first thing you need to do is find the bottlenecks and fix them. You can fix as many of the looser areas as you like, but the general design will barely change. This is something I have come to understand on a deep level. It’s one of the reasons I was so comfortable working with computers.