The thing is, the narrative you've created is alost entirely self-created. The way we see Shepard talk and react with his companions doesn't show us the relationships. The thought has gone into them, and I can see it;s there, but because all we actually see of the growth between any two people in Mass Effect is, essentially 4 conversations and a loyalty mission, it doesn't feel at all human or natural.
And they are entirely passive, no matter who you are, you can convince any member of the crew (of the right sex) that they are in love with you, even if they're strong upright people and you murder kittens. They don't respond to who you are, or how they see you act in the wider world. They respond to you not saying they look like a hag when they talk to you. If you even care for your crew a tiny bit, you end up with three ladies trying to have sex with you, they are so frickin' passive that you can just say, actually I don't want to have sex with them, I'll have sex the other lady, actually I don't want to have sex with her, I want to have sex with you, and they're fine with it. You can even do this as many times as you like if you feel a bit indecisive.
KotoR 2 was so much superior in every with this. Not everyones motivation was sex, when they got to know you, it was normally that they saw something deeper in side of you, they would respond to who you are, what you did, how much time you spent with them, whether you were a douche to other people. They had interesting personalities to explore as you gradually gained their trust, and you had to work to gain their trust. Because people were more complicated than sex or nothing and because sex wasn't the goal, but often letting you train them to be a Jedi, getting over their deep resentment, and because time was limited you wouldn't really get in the situation of having five people hang off your every whim
In Mass Effect, you remember they exist 4 times and they're yours as you please and the focus is so often on sex over relationship. Even people with whom it doesn't make sense try to get into your pants.