Okay since this seems to need to be an actual thing because this fanbase does not seem to understand what reading comprehension is:
The sex that is shown in MDZS, especially the first one is not at all meant to be titillating for the reader. It is supposed to be virginal cringe bad sex but they get through it cause, heeeey, that's what actual sex is like at first if you love and are attracted to the other person! It even mentions Wei Wuxian's ass is getting sore from being on the ground too long but he's caught up in everything else. And they love each other simple as that, not deep at all.
Not all written sex is meant to be so very very beautiful for the readers. Otherwise that's how you get eyeroll worthy things like 50 Shades that is trying, in all god's green earth, to BE SEXY, with no awareness.
And as to the kinks issue, surprisingly, a lot of people in real life have some very very dirty kinks, humans are weird they like strange morbid things during sex even when consensual. It would really be fetishizing if Wei Wuxian and Lan Wangji shared these facts with anyone else but they don't, it is meant to be private and their domestic routine like any other weird couple that would get the side eye in society for talking about their kinks to others.
