Things like contraception etc must be dealt with slowly. I would require all Priests to teach against it. God forbid that anyone keeps continuing in grave sɛҳuąƖ sin, but even if a Catholic sins during the week, confesses his or her sin, and then goes to Holy Mass and Holy Communion with the resolve to change, he or she is still a Catholic and can do so. A dogmatic anathema against contraception may follow later, once Catholics have, by frequenting the Sacraments, praying the Rosary etc, been led away from sin. Saints say you cannot keep continuing praying the Rosary and persisting in grave sin. You will give up one or the other.
You will always have people who have decided that they are going to live in mortal sin for at least a portion of their lives. They gamble
"I'll take the chance I won't die anytime soon, then when I'm done [doing whatever it is they feel like they have to do, or see themselves as too weak to give up], then I'll make it right with God". That's a huge problem, but that's
not the problem most so-called Catholics in our time have. Their problem is far worse. They actually assert that what they are doing is not wrong, that they know more than the Church knows, that what "society" or "modern times" have to say about the matter is more important than what the Church teaches.
There are two things going on here that cloud their judgment --- money/finances/convenience/desire for an easy life, and that fact that this sin involves sex. With regard to the latter, "the heart wants what it wants", and other things want what they want as well.
It's no more complicated than that. (I doubt that many have thought far enough ahead, to say
"if I adhere to this teaching, I may never be able to get married, because I won't be able to find a spouse who will go along with it". People generally don't think that far ahead anymore, if they ever did.)
If they were just willing to say
"I know this is wrong, I know this is a mortal sin, but I don't love God enough to avoid it, I don't trust God enough to try to live by it, we can't take a chance on that extra child, I can't lose my spouse, and besides, my gonads can't do without sex" (the latter would be far more true of males than females), then that would be bad enough. They certainly don't cease to be Catholics, they have just made the decision to be Catholics who are willing to live in mortal sin for a time. But to say "the Church is wrong" or "this doesn't bother my conscience", well, that's ten times worse. There's no coming back from that, because not only do you have the sɛҳuąƖ sin itself, but you've also introduced an element of pride, fueled by a world that doesn't see anything wrong with it.