The paper hits the nail right on the head, but it misses the mark on the next constraint: how to decide what to build.

In the old days when writing code took up a lot of resources, the constraint was self-correcting since being off in your implementation was obvious enough that the error could be easily seen after three months of work on the wrong feature. Today, you could spend five wrong efforts in the same amount of time that it used to take you to implement one wrong effort.