Class S was an important genre normalizing love between girls and expressions of love between girls, and it told an important truth that lesbians and bisexual women of the time went through, which is being forced out of their relationships outside of school and expected to marry men. It also kinda fucking sucks, and I sure as hell don't want to read Class S works, and it left a massive imprint on the genre to this day, almost every long-form manga references the concepts of Class S, usually, thankfully, to refute them, but still having to acknowledge them. It also influenced the setting, a massive amount, I think we can agree. And the open-ended endings of the oneshots to which MacySan is referring are an artifact of that, I'd argue, by not showing the girls in relationships beyond those in high school, a sense propriety is maintained, but I'd say that's a minor part of things. Either way, you're both arguing pretty hard for having viewpoints that don't actually fully conflict with eachother.