I have a good friend whose favorite saying is, “Everybody’s Catholic, they just don’t know it.” I think there is some truth to it.
But for legitimate ecumenism to occur, the RCC might not have to alter its doctrine so much as it needs to be more inclusive and welcoming of those of other faiths. After all, like Bishop Sheen said, “there are not a hundred people in the world who hate the Catholic Church, but there are millions who hate what they think it is.”
My two cents.
Edited to ask the question, How many of you (Catholics) have listened to someone run down the RCC and you know they have no idea of what they are talking about because the only information they have, comes from those who have a reason to cast half truths and completely false understanding.