Hi, thanks for your comment!
DW isn't supposed to be set in a world where gender/sex don't exist - we simply wanted the MC to be a character who can be absolutely anyone. I agree that it isn't a perfect system, but it's a choice we made and stuck with throughout development. It's possible that I will have time before the spring update to add more pronouns, but that depends on workload and many other factors.
As for Vincent's route, it's very much intentional that he uses the word "wife" for the MC. Built into Vincent's character is an emphasis on conservative family values and family structure, and thus he uses the word "wife" because that is the role he wants to force MC into. Yes, he may very well be forcing the MC into an impossible situation if the player imagines an MC that isn't physically capable of making a child with him, but Vincent doesn't care. It isn't about the actual act, it's the sentiment behind it.
And, yes, MC is a bit nonchalant about this, but they are also in a very strange, dangerous situation, and I imagine being called the proper spousal term is the least of their worries.
We talk about Vincent's values more in-depth in the walkthrough, so if you want more information on the rationale behind this decision, you should read Vincent's character information (especially the detailed essay portion). You can download it here on itch, but if you got the game on Steam, you can get the walkthrough on our website for free.