> Marriage is about declaring to your social group and each other you’ve decided to strive and commit to something greater than yourself.

I think most people can accept this belief while still thinking that there ought to be an out for two people who find themselves deeply unhappy together for a long period of time. Committing to something should very rarely be an absolute thing, and most people (even those who accept and respect marriage as a social institution) don't think that marriage should be one of those things. That's compatible with thinking (as you say in your OP) that most romantic relationships are shallow and not ultimately very meaningful, and wanting something more.