I'm going to crosspost something Kyrieru said yesterday about struggle mechanics in their thread for Lufuclad, which i think is rather relevant to this discussion:
That said, I think almost all struggle mechanics based on mashing, quicktime events, rhythm, are all equally pointless.
It's sort of like how some of the best H RPGs are ones with almost no combat. If you aren't going to put in something meaningful, at least put in something that isn't slow and tedious, or adding challange out of the player's hands. Otherwise people will just cheat or use saves. The gameplay has to add to the H in such a way that playing is more fun "and" a better way of experiencing the H than cheating or saves.
I have the same mentality about struggle systems. To me, an actual struggle system should be tactile, based on visual character animation, or based on thematic stats that have more than one desirable outcome other than sex/no-sex. Because I can't do anything meaningful yet, I prefer to at least make it simple and easy, and mashing is at least slightly tactile, whereas quicktime events are not. At this stage people only care about H, and so it's better to just give players the choice in a slightly thematic way.
One of, if not THE reason to play h-games is for the H-animations. That is why people are here, rather than playing skyrim or dark souls or whatever. Anything that interferes with that, be it making it too challenging to access some animations or just that parts of the gameplay are outright tedious will actively harm the game, and incentivise players to cheat or seek out savefiles so they can skip to the gallery, essentially wasting all the time the developer has spent on making the game part of the h-game.
Obviously, this is not a desirable outcome.
This is why the vast majority of h-games are easy. most game devs deliberately made it so you don't need to savescum, or even really strategise in battles or plan out your build, because that would detract from the primary draw of the game. Likewise, developers need to be careful when creating mechanics that interact with their h-animations, because if the game hampers the player's enjoyment of the hentai, the players will just skip or cheat through the game to get to what they really want.
As a system, struggle NEEDS to enhance the h-animations, not hinder the player's enjoyment of them. And lets be honest, that's actually really hard; anything that is going on peripherally to the animation itself is going to draw attention from said animation, be something as minor as having to mash a button, or something more complex like having to quickly recognise and input a series of QTE commands. Looking at things from this perspective, i do agree with Kyrieru in that neither of these really add to the h-animation itself, and if that's the metric you're using to determine worth then yes, both systems are kinda pointless, at least beyond the point of giving the players the yes/no choice of: do I want to see this animation?
With regards to actually making a system that enhances the h aspects of a game? I have no idea. I don't have any experience in making any kind of game, nor am i knowledgeable about the theories of game design or the psychology of gamers.
But if you can't make a system that enhances your games primary draw, then at the very least it shouldn't interfere with it. Hence the struggle system that so many use. It's not the best thing they could use, but it's a low-effort solution that doesn't harm the game, and being low effort it let's the developer focus their attentions to where they CAN measurably improve the game.
Edit: Actually, I just thought of a good example of a struggle system that would, by Kyrieru's definition, add to the hentai aspects rather than detract:
Kunoichi Botan, and specifically the half-oni guards that are the standard h-enemy of the game.
The struggle system for this enemy is interesting because it isn't just a matter of mashing the escape option. Instead, the player has a series of options, one of which is an attack option that will instantly kill the enemy and end the battle.
But only if it succeeds.
The gameplay of this encounter is all about managing three stats: escape chance, lust, and the enemy's orgasm meter. Escape chance starts low, and you only get one shot; fail and the enemy will kill you. to avoid this, you have to use the other options, which let the enemy molest you, or intensify the severity of the h-encounter, going from groping the breasts through intercrural all the way to penetrative sex. The more severe the sex action, the faster your escape chance rises, but the faster your respective lust bars rise too, providing a balance of risk and reward.
If you let your own lust fill up, Ajisai will cum, and doing so too many times will cause her to give in, ceasing all resistance and preventing the use of your surprise attack. If you let the enemy cum, they will creampie Ajisai, which due to specifics of the story that I'll not go into leads to a game over. This provides a number of possible outcomes beyond the simplistic sex/no sex that button mashing gives you: you could die by attacking too early and fluffing your attack roll, cum too many times and give in to your own lust, stall too long and let the enemy finish inside, or succeed and strike down the enemy in their moment of distraction.
I really enjoyed this mechanic, and despite the game having a galley I much prefer to reload one of my saves and revisit the battles when going back to this game, as they're fun and engaging. There's also a sort of meta-game for those who are playing the battles as part of the game, rather than in the gallery: You don't want Ajisai to die and set you back, but you also want to see the hentai, so how far can you push the severity of the h-battle before you take more lust than acceptable or risk losing? The game even rewards this, because there's a point roughly halfway through the enemy's orgasm meter where the enemy will try to initiate penetration. You have the options to allow it (bad, because counterattacking during penetrative sex is harder), try to avoid it, or counter attack while he tries to insert. Counter attacking during this action gives a bonus to your chance of killing the enemy, rewarding this sort of playstyle.