Read enough of this material and a clear pattern appears. Scenes that work and scenes that do not are frequently equally explicit, equally well drawn, and equally competent technically. The difference is structural, and it comes down to whether the scene is doing anything beyond depicting an activity that the reader could have imagined without help.
Naming the differences is useful because they are all fixable. None of them require better drawing, and none of them require the scene to be more or less explicit than it already is.
Stakes make a scene matter
A scene where nothing is risked is pleasant and forgettable. Stakes can be small: something might be admitted, something might change between two people, one of them might realise something she would rather not. Without any of it, a reader watches events rather than following a situation.
Stakes usually come from what surrounds the scene rather than from inside it, which is why explicit scenes dropped into stories with no relationship material rarely land. The obstacle argument in the chemistry notes is the same point from a different angle.
Something has to change
The scene test from the piece on what makes a scene applies here without modification. State in one sentence what is different at the end. If the answer is nothing except that some time passed, the scene is decorative, and readers treat decorative scenes as skippable however carefully they are made.
The change need not be dramatic. A shift in who is in control, a piece of information exchanged, a decision made that cannot be unmade. Small changes accumulate across a story and give a sequence of explicit scenes a shape rather than making them interchangeable.
Both people have to be there
A large number of weak scenes have one character present as a person and the other present as a body. She has no reactions that change anything, no wants of her own visible in the staging, and frequently her face is out of frame for most of it. That is a scene about one person, and it reads as thinner than its page count suggests.
The fix is the choreography described in the piece on visible consent: attention flowing both ways, initiative changing hands, responses that alter what happens next. It improves the work and it happens to be the responsible way to build the scene, which is not a coincidence.
Specificity beats intensity
Generic scenes escalate; specific ones observe. A detail that belongs to these two characters and no others, a habit, an awkwardness, something said that only makes sense between them, does more than any amount of intensification. Readers remember specifics and forget intensity almost immediately.
This is the same particularity argument made in the piece on the nude and the naked. Interchangeable bodies produce interchangeable scenes, and interchangeable scenes are hard to care about for more than the time it takes to read them.
The surrounding material does half the work
A scene inherits most of its weight from what came before it. Two characters whose relationship has been established over several chapters bring all of that into the room with them, and the same scene between two characters the reader met on the previous page has nothing to draw on. This is why the identical scene can be gripping in one book and inert in another with no change to a single line or panel.
The practical consequence is that improving explicit scenes often means writing more of everything else. When a scene refuses to work after several passes, the problem is frequently upstream, in the chapters that were supposed to give it something to stand on, and no amount of revision inside the scene itself will supply what is missing.
Pacing is usually the hidden problem
When a scene feels flat and none of the above is obviously missing, the problem is often duration: the scene sits too long at one emotional level. The beat structure and variation described in the piece on pacing applies to still and sequential work as much as to animation.
The quickest diagnostic is to list the beats and their lengths. If they are all similar, the scene has no rhythm, and a reader experiences that as monotony regardless of what is being depicted.
Building a scene that is worth reading
Give it stakes, make something change, keep both people present, choose specific details over intense ones, and vary the pacing. Five things, none of them about explicitness, and together they account for most of the difference between memorable and forgettable work in this area.
Characters here are fictional and unmistakably adult, as set out in the reader agreement.