Here's an angle on doing creative speed I didn't think of. It's not about getting more done in the least time-cost.
It's about the ability to do rapid experimentation, and the self-imposed perception of time-cost.
Slowness seems to make a special contribution to this picture in our heads. Time is especially valuable. So as we learn that a task is slow, an especial cost accrues to it. Whenever we think of doing the task again, we see how expensive it is, and bail.