I like this thinking because it's a true reflection of how things work. I strongly doubt any housebuilder goes back to the architect and says "can't do that, foundations bad." They'd explain what the problem is: maybe the design is rated to a certain weight/height, or what's in the ground composition that prevents the requested changes.

We should do the same in software engineering. What exactly in our design (e.g. that Perl script that's running half the operation that we need to investigate) is stopping us?