Pope Francis has formally approved allowing priests to bless same-sex couples, with a new document explaining a radical change in Vatican policy by insisting that people seeking God’s love and mercy shouldn’t be subject to “an exhaustive moral analysis” to receive it.
Catholicism IS Christianity. If you were to disassociate yourself from the Catholic Church as many have done over the years and also insist on the difference being “Christian” and “Other”, then Catholics would be the only Christians, as your diversion would be the other. I understand your meaning that you believe your sect of religion is the “correct one” just as any follower of any religion does, so you can call yourself the “correct Christianity” if you’d like but saying ”Catholicism isn’t Christianity” is factually incorrect.
Put simply, either Catholics are Christians and so are you, or Catholics are Christians and you are not. Separating your Protestant/Evangelical beliefs from the Catholic Church is perfectly understandable and that I wouldn’t criticize you for doing, but separating the Catholic Church from Christianity is fundamentally impossible.