Well I agree with you that vast swaths of Catholics disagree and/or ignore the teachings on contraception. And many priests/bishops are loathe to bring it up if it is at all unavoidable. But that doesn’t meant that they are correct in doing so.
And if the Church does indeed change the teaching, then the Church would be teaching in error, either in the past, or in the future. In which case the entire moral foundation of the Church would collapse, since if they could be wrong about this, then they could be wrong about any number of things.