Focusing on games rather than porn in general:
Fighting the PC/avatar: "Game Over rape" games are the poster child. The game's narrative and gameplay are perfectly consistent but they directly oppose the actual goals of the player at least as far as porn is concerned. Virgin runs without a gallery unlock count too. Also any time an option is presented but the PC outright refuses to follow through, with the exception of "corruption" games where it becomes available later and the refusal acts as a hint.
Ludonarrative dissonance (or "inconsistencies between story and gameplay" for normies): A staple of non-pornographic games as well but still applies to sex scenes. If a character loses their virginity early through an optional encounter they can not do so again later in the main story. If the previous scenes allowed a character take an arm to the elbow they should not worry a realistically sized dick might be "too big" for them. If I'm a lvl99 Succubus Archmage I should be able to do something against that noname scripted mugger other than stand still and squeal.
Narrative/gameplay-internal inconsistency: similar to the previous one only sometimes they screw it up even without the second component. Not planning for someone to grind to max level and beat the optional superboss before completing even half of the main plot is understandable, but if a character (usually female...) is introduced as a badass warrior fighting off multiple opponents without the player's input they DEFINITELY shouldn't be freezing and stammering when confronted with a drunk doofus or alley rapist. On the gameplay side most might be due to poor QC but all too often one scene will let you cum unlimited times while another ends after the first orgasm.
Grind: sucks the fun and immersion right out of whatever content you are forced to repeat, even worse if it involves the sex scenes. Add RNG in here too because as far as I'm concerned it's exactly the same only with the extra step of repeatedly reloading a previous save thrown in. Unskippable repeats probably also fit for being meaningless padding although those are a bit of a grey area when it comes to broadcasting mechanics (using OP's example: a "kyaa! *water pour* *water pour*" image popup or short animation would be fine by me but if she stammers about the embarrassment for 30s while rubbing her crotch every single time that would be too much in my opinion)
Faking gameplay: I guess many walking simulators fit here, but I don't just mean being grindy and boring. Basically some "games" would be fine and in many cases even more enjoyable if they had no real gameplay or interactive elements at all yet shoehorn them in. For visual novels this would be illogical trial-and-error choices leading to immediate Game Overs, with RPGM they like to throw in cookie-cutter battles and maps which do not add or even hinder their worldbuilding, old flash games like to stall you on a pixel hunt segment which you beat by holding down Tab.
As far as actual porn content goes it's really subjective and since I don't like most forms of rape/coercion/blackmail, humiliation and general "being shitty" (verbal abuse, cheating, harassment/groping, sleazebags) I'm definitely biased here but in most examples of those I've seen (again keep in mind I don't play high-quality NTR games because I don't like the content) they tend to fall under my previous points as well: rape victims don't even try to fight back even against a scrawny kid that's a head shorter than them, blackmailers don't get punched in the face, some people develop Tourette's the moment they become aroused and their partners don't seem to care or notice, the more raunchy sandbox-y games sometimes let you freeroam with your fling or even have sex right in front of your SO without being "found out" (because it's limited to a scripted scene or an RNG trigger...) and groping usually takes the form of a "point grind" where you suffer no negative consequences and doing it enough actually makes the target like you.
