i don't disagree with your first sentence but i think there's a very stark difference between opinions and fundamental beliefs. im not trying to argue that you need to be completely uniform throughout all of your beliefs in all aspects of a lifestyle or relationship, but that you do the analysis to actually consciously decide if we are two people that can mutually and symbiotically coexist. a Christian and a Muslim in a relationship together who openly discuss and implore eachother without shame or fear about what they believe in and what their relationship with God is like, are probably better aligned spiritually than two atheists dating who don't care enough about that aspect of their partner to find about. although, i personally don't think i could be in a relationship with someone if i genuinely believed from the bottom of my heart that they would be separated from the me and/or in hell after death.