OP, marriage is nothing to do with romance. That is just a fairy tale spun to women to get them to do it. The big dress and all that.
If you disagree, consider this. You can be in love without being married. You can be married and not be in love. Therefore it is impossible that marriage and love/romance are tied to each other.
Marriage is a legal contract that involves the merging of assets, rights and responsibilities, and contains within it the terms of its own dissolution, ie it sets out not just how these things are merged, but is part of a legal structure that anticipates how they will be separated, should the marriage end.
There are very good reasons to want to be married ---- and they are all to do with the legal and asset/financial element. Your DP seems a bit horrible, but he is at least thinking in a clear-headed way about what marriage is, ie a legal and financial contract. I would engage with him on these terms. A relationship is a partnership or should be. It should benefit both parties equally (not necessarily in identical ways, but equally).
If you feel your relationship does not benefit you as much as it does your partner, and marriage would correct this, put that to him. If he doesn't care about that sense of equal benefit, then he doesn't care about being in a partnership. Which makes him no partner at all.
Going to him with an argument about romance is just talking at cross-purposes.