It is not debatable - see my points below.
and remember that the teaching of the Church are not simply the Church's opinion on the subject.
I would like to first point out the following in the Catechism of the Catholic Church.
2399 The regulation of births represents one of the aspects of responsible fatherhood and motherhood. Legitimate intentions on the part of the spouses do not justify recourse to morally unacceptable means (for example, direct sterilization or contraception).
as we can see here, the Catechism first calls contraception "Morally Unacceptable" Regardless of intention.
2370 Periodic continence, that is, the methods of birth regulation based on self-observation and the use of infertile periods, is in conformity with the objective criteria of morality. These methods respect the bodies of the spouses, encourage tenderness between them, and favor the education of an authentic freedom. In contrast, "every action which, whether in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, proposes, whether as an end or as a means, to render procreation impossible" is intrinsically evil:
Here we see that the Catechism quotes Humana Vitae in saying that contraception is intrinsically evil. This is important because Intrinsic means by its nature, it is evil. This can never be good as evil is in its design.
The reason it is evil, is that the sole object is to render procreation impossible.
1756 It is therefore an error to judge the morality of human acts by considering only the intention that inspires them or the circumstances (environment, social pressure, duress or emergency, etc.) which supply their context. There are acts which, in and of themselves, independently of circumstances and intentions, are always gravely illicit by reason of their object; such as blasphemy and perjury, murder and adultery. One may not do evil so that good may result from it.
We see here, that the the morality of the act cannot be judged solely by the intention. Here we also see that there are objects, which are always gravely illicit regardless of their object or the intention.
This implicitly includes contraception as it is intrinsically evil due to its object which is to render procreation impossible.
So now we see that regardless of intention, or circumstance, there is no way one can use contraception for any reason in good conscience.
Now that we have determined that the object is always seriously evil, we only have left knowledge of that information and free concent to determine if one is guilty of a moral sin for using any form of artificial birth control.
Not everyone who uses artificial birth control is guilty of a mortal sin.
That is due to lack of knowledge or concent, but not lack of serious matter.