“Makes no sense whatsoever. So everyone can make up what they want to believe.”
That’s a straw man argument, made up by you, not me.
It only means that other Christians do not have to accept the Roman Catholic Church as “the only true Christian Church”, nor do they have to accept many Catholic practices as Christian.
Not at all. Look at the words of Christ:
Jesus answered, "I am the way and the truth and the life. No one comes to the Father except through me.” John 14:6
There can be only ONE truth. Taught by Christ, through the Church Christ established. A Church that has existed for 2000 years. The Catholic Church.
There cannot be multiple truths. There is only one truth.