Part of the problem here is that the Church's ability to control sexual behaviour is declining faster than its ability to block access to protection.

It's an empirical question though. In societies with large Catholic populations, is it actually difficult to get access to birth control.  Statistics I've seen before on abortion would indicate otherwise. (I think Guttmacher Institute.) In Catholic Latin America, even where abortion is illegal, abortion rates are higher than in many less Catholic countries where it is legal, which means that we have no evidence that access is difficult even if where nominally prohibited.  Also, where, in Africa, Ireland, or anywhere, is it difficult to get access to condoms today? This would seem to indicate that the Church's ability to block access to protection is a bit overblown.