Furthermore, your suggestion that we “can’t say the couple sinned” cannot imply that neither sinned. It might be understood that their may be an innocent spouse, regarding the contraception. That much I have not argued with, at all.
I am only arguing that those couples who do contracept are not allowed to do so by Church Teaching. Save for medical or health reasons unrelated to the intention not to conceive.
There are no exceptions to the moral law of the prohibition of contracepting pregnancy.