While I could be the poster child for RP-without-intercourse (that's where I spend 97.4% of my word count), I'm kinda gobsmacked by that statement. With all the different characters, attitudes, relationships, locations, positions, equipment, kinks, sights, sounds, smells, and sensations to describe in any given sex scene... I have trouble picturing it as boring.
Ah, but I wasn't referring to characters, attitudes, relationships, locations, positions, equipment, kinks, sights, sounds, smells or sensations... In fact, you have rather made my point for me.
Because, the way I see it, to have any of those things meaningfully in a sex scene, unless you are just going for deus-ex-machina
type of thing, you need to have a back-story.
Example: One of my favourite kinks is watersports. But to have my character suddenly pee on her girlfriend during sex for no reason whatever just isn't going to work. There has to be a reason. Equally, one of the most frustrating (IMO) plots is the sudden change from normal sex to BDSM sex. Because unless you are a magician you cannot suddenly have a bondage dungeon in your house where there wasn't one before. The "Lets try out some BDSM stuff" scenario really doesn't work very well because it requires the characters to improvise what they use and it's far too tempting for the writers to magically produce a pair of hand-cuffs or whatever.
I know this from being tempted to do so myself!
To have a decent BDSM sex scene the D MUST already have her "play room" set up, which means there is a history, even if it is implicit.
Now, to address the things you listed that best make my point for me : Characters, relationships, locations.
In order to establish a character and make her credible, it is necessary to tell the reader something about her. And not just that she makes a lot of noise while having her orgasms. That doesn't say anything about her character.
Relationships are something that develop over time. So unless the relationship is "Rapist and victim" there has to be some history between the two characters - in fact, even with a rapist and her victim, there is an implicit history: Why did the rapist chose that boy? how long has she been following him, etc...
Yes? No.... of course not. Come on, describe the room. At the very least describe the damn bed, yeah? The more exotic the location the more detailed the description needs to be so that the reader can picture it.
So, what have we got now?
We have several posts establishing the characters, several more defining their relationship to each other, a couple describing the location, a couple describing how the characters got to that location, some posts detailing why certain kinks are in place, and no one has even taken a garment off yet...
And guess what? ALL of the above stuff is a great big fat turn-on to myself and a lot of other players on E.
But what is a massive turn-OFF is when we go to all the trouble of creating the character, the scene, the relationship, the environment, and all our writing partner does is post:
"Ellie moaned and thrust her hips forward".
And yes, I have had that happen a number of times! Yes I'm exaggerating a little, but I'm sure we've all had the one-liner reply?
Then there is the player who extends the first sex scene beyond what is logical by refusing to have an orgasm. And of course, the one who is ONLY interested in that sex scene, shows very little enthusiasm for descriptive writing until you get there, and then the moment that first sex scene has happened, just drops the RP.
I like a well written sex scene as much as the next pervert, but I like a nice big side order of story with it.
I think I can summarise my point best by saying this:
All those things Madmartigan mentions, that he says provide variety to a sex scene and make it interesting, are unavailable to you unless
you have a story in place! Or, perhaps more accurately, unless you have a story, your characters are one dimensional, their attitudes are fixed, their relationship is stagnant, they are confined to one location, have no reason to explore different positions, have a limited amount of equipment available, have a fixed number of kinks, see the same old sights, hear the same old sounds, smell the same old smells and feel the same old sensations, for the duration of the roleplay.
So unless your RP is limited to one sex scene - in which case, as I already pointed out, it is a one-shot, writing repeated sex scenes is very quickly going to become monotonous.