LOL, if they don’t oppose the other doctrines, why not fellowship and worship with each other as the Bible commands in John 17 and 1 Corinthians 1?
LOL, many CATHOLIC "sects" are at odds with one another. Even within the RCC, many congregants, many more, percentage-wise, than can be claimed by most fundamentalist Protestant sects, deny the basic teachings of the RCC. Numerous recent polls show that a very large portion of Catholics don't even believe the very basic doctrines of your faith. A majority don't believe that illicit sex, homosexuality, same-sex "marriage," contraception are sins. And don't try to disclaim those with these beliefs. You own them by your admission.
Talk about a divergence of belief.