Why not define perfection, for our purposes, as achieving the results you set out to achieve?
If you set out to build a model that is as reasonably accurate as can be expected in the scale you're working in (it varies enormously, of course), with good fit of parts, a finish that represents well what you wanted to represent (gloss or patina, etc.), and mechanical elements that could actually work in reality...all with a consciously defined level of good-enough...fine. You've achieved what you set out to achieve.
If you set out to assemble a model without correcting flash, sink marks, paint everything with a brush and leave the brush marks showing, and aren't bothered by glooey fingerprints on clear parts, wavy masking lines, and some parts on backwards, then you've also achieved what you set out to achieve.
EDIT: Trying to define perfection is like calculating pi. No matter how far you go, you can still go farther. The goal is unattainable because it's infinite, but it might sometimes be of interest to see how close you can actually get. For me, 3.14 is usually "close enough".