no one flippantly calls game of thrones or rated r movies porn even though many of them have a far larger ratio of sex and nudity to non-sex sex and nudity scenes than you will find in fate/stay night.
fate stay night is a 90 hour visual novel with a few short sex scenes that are effectively bolted on after the fact and are even cut out entirely of most releases of the game at this point.
I remember just fine when the translations for Tsukihime and FSN were released. I remember fine when Fate/Hollow Ataraxia was released. Nobody was deluding themselves
Everyone knew just fine this was porn with pretty decent story attached to it. Rance and MGQ had good enough gameplay attached to it, but everyone knows its for porn.
I remember when Mahoutsukai no Yoru was released and everyone begging to figure out where the porn was. Last time i checked, a TL still hasn't been released a decade later, no porn as a reward.
Yes, the game has been edited to be family friendly and vanilla at this point, but it doesn't change the fact that it was originally released as hentai, Nasu's ability to compare genitals to oysters be damned.
A great many of today's fans have never encountered the sex scenes. They're a tiny fraction of the original game, they're well-known as not being particularly erotic or well-written; they're really not important or relevant to the game's history or sales. A couple of sex scenes don't make a game "porn" any more than a couple of quips make a game "comedy". That you focus on them says more about you than it does about FSN.
One out of Clannad and Kanon has sex scenes in and the other doesn't. I can't even remember which is which, and it doesn't matter.
Sex sells, and is an important part of boosting attention to a product. Yet the game and series makers spend 99% of their time on the rest. Games with sex and tv series with boobs abound, the reason Fate SN or GoT succeeded isn't "because porn", even if it was part of the original recipe.
I feel like the fact that stuff like Fate and Tsukihime get all-age releases on home consoles is some data point to consider. That and the fact that F/SN is an amazingly long thing (like 50+ hours of reading?) for the handful of scenes... I mean that's a lot of work if it's for a CG pack!
Mixing good storytelling with porn in a visual format is really hard to do well. One or the other inevitably suffers. As someone who is pretty far into demisexuality, I would love to be able to find something visual that's more stimulating than erotic literature. The best compromise I've seen is 3d animated visual novels coming out of a select group of small indie studios. This still leans far more heavily into story than porn, the animation is repetitive and not very sexy at all, most of the time I skip through the sex scenes to get back to the story.
I guess if you're super-easily stimulated then you can look at any kind of serious video game with erotic elements as porn, instead of just as a sexy story/game. But if I want porn, I want porn. The moral element is unhelpful.
fate stay night is a 90 hour visual novel with a few short sex scenes that are effectively bolted on after the fact and are even cut out entirely of most releases of the game at this point.