That, of course, is not the CDF’s argument. Let’s look again: the word “perfection” is modified by the adjective “proper”, which tells us that generating humans outside of the conjugal act substitutes an improper perfection for a proper perfection, not imperfection for perfection (which is what Savage infers).
How is this perfection “improper”? It’s improper because IVF reduces the child to “the product of an intervention of medical or biological techniques … an object of scientific technology” (DV, II:4c). Even if every questionable technical aspect — destruction of unused embryos, masturbation — were taken out of the equation, it still “remains a technique which is morally illicit because it deprives human procreation of the dignity which is proper and connatural to it” (II:5).
In other words, by its very nature IVF treats the child as a consumer good, made in a factory. That's an intolerable offense against her dignity as a human person, which no claim of entitlement can in natural justice overcome.
As hard as Savage tries to make it sound like a pure love of children which drives the act, his own words hint at the real motivation. Not just any child would do; otherwise the Savages would have turned to adoption. No, the child had to have their genes, not somebody else’s. Again, the unspoken assumption of entitlement spoils and corrupts what would otherwise be a noble sentiment.