My mom's a lawyer. One of her teachers used to say: "If you livin' with someone, marry em'. If you stop living with someone, divorce 'em"
The subtext there, is that before anything else... Marriage is mainly a legal/political artifact. It's one of the ways to share goods with another person sustained by the law and also, gives other important beneficts (Depends on coutry). With that logic, we should be marrying our roommates/friends if the level of trust is enough to share goods, medical insurance and other stuff even if we don't love 'em that way. That said, most millionaire couples don't share properties anyway, rendering marriage as useless a merely formal thing.
So, there's that approach. Not that I've done it myself. But I think it is healthy to have a legal marriage with the person you are living with if they are not your family (boyfriend/girlfriend/friend)
Is not like people always marry because of love (The idea is kinda new), and not doing it in a grandiose bombastic way it's fine too!