I think what you mean to say is that the missions leading up to a successful romance are well written and they are. I LOVED Judy's romance and all the missions leading up to it, but AFTER I had completed her missions and successfully romanced her it all died so quick. Barely a text from her, just a few new dialogues exhausted very quickly that goes on repeat forever and still no physical interactions with their own dialogues. The romances are done well to a certain point, but don't call them finished products. For me and so many other people, a good romance that is with you all the way and always present in some way shape or form is what makes the greatest impact on a player's experience of the game as a whole. In Mass Effect I had to play around my choice of romance if I had any, and there was always some interaction, new dialogue as you progressed and just tons of little details that helped me get super immersed in the game.
I am NOT happy with having played such a great story line only to see it die like rotten fruit pretty much immediately as it finished leaving me with what..? A partner? Someone I can call to say the same 3 repeating lines to? Someone who just sits in their apartment doing nothing, being available for nothing?
So yes, the romances are nice and the missions are amazing, but AFTER that it sucks blazing donkey-cockles.