That is a huge failure on the medium then. A huge failure.
It's easy to say something is a failure for not doing what you want, but I don't think there's much value in it. I rather think about why things are the way they are rather than go into it with condemning preconceptions. I think the issue is that you are working from the top down. You begin with the idea of "videogames doing things movies (etc.) do" rather than "what are the things games do".
I have to wonder: what does a "pure" romance videogame look like? Most likely a little more than a series of dialogue choices and maybe some small miscellaneous fiddling with the environment (so a dating sim?). At some point it begins to look like additional step to seeing people talk to each other, a laborious method of exchanging information despite the information being the point, like having to push "play" on your TV remote after every line. Although the opposite sentiment exists (and arguably exactly what people want exists, likely in some overlooked low-budget games), this is easily seen as sacrificing interactivity for the sake of passively presenting something that can be done much better elsewhere. This is what I would call a bastardization, something I would rate unfavorable in comparison to what has already been accomplished with games already (even if it is only within the area of "war") even if it manages to escape the practical "limits" of the medium (but not really, once you begin to think of the whole thing as a experiment of choosing the right options to get the best ending, a happy ending).
I would say the most illuminating fact on the matter is that we do not actually speak or have conversations in the physical or mental sense within videogames (with some truly abyssal exceptions, like "Facade" and "Hey You, Pikachu"), we choose fairly basic options in a fairly basic way. Having a conversation, how words are said and how they are taken to mean seem infinitely more complex than walking through a series of conversation trees (which then to go on to compare quite unfavorably to what has been accomplished in strategic and reflexive possibility spaces). When we can recreate what it feels like to have a conversation, one you'd find in a movie or, much better, real life, then you end up getting something natural, probably while wearing a VR device and a mic.
On the other hand, if you give the player the role of being an actor in a romance plot, will they be as good actors as the professionals? And are people ready to fall in love with fake people rather than watch fake people fall in love with each other? Well, this is an anime game thread, so...
What I find a little more bemusing is the idea of a "mature" erotic game looks like. Is it this like comparing X-Art to Bangbros? So, that's probably a VR set, a mic, and sex device attached to your genitals.
Sounds juvenile no matter how you cut it, but isn't masturbating to porn juvenile? But what if most adults do it? Are we to assume acting on your base, instinctual, shallow sexual urges is juvenile? Are most adults juvenile? Then that's a really odd definition of juvenile. Here lies the crux of the matter when it comes to "maturity" and "juvenile": it's simply saying "I want people to be like *this*" (e.g., "I want people to marry, have two kids, and buy a house - and not watch superhero movies for fucking kids"). "Maturity" is the model of the ideal adult/citizen. "Juvenile" is a way of venting the negative feelings that come about when reality doesn't match the expectation. This is why I say it's easy to say something is a failure for not doing what you want, but I don't think there's much value in it.
