"You are the salt of the earth. But if the salt lose its savour, wherewith shall it be salted? It is good for nothing anymore but to be cast out, and to be trodden on by men." (Matthew 5.13)
Of what use would it be for Catholics to become just another bunch of mushy "it doesn't really matter what a man believes so long as he is good and honest in public" types?
To soothe your consciences?
I am a Jew. We haven't historically fared well at the hands of a triumphalist Catholicism.