I disagree that non-obvious game overs make it a game. Those cases aren't really choices or challenges if the player isn't made aware of them or has no way of influencing the outcome.
It will depend on what you call "non obvious" here on whether we can agree. Should the golden path be communicated clearly to the player beforehand so he'll find it on his first playthrough or can it be one of several actions which all make sense in context of the game, its mechanics, and its story? If it's the former, we cannot agree, if it's the latter we can. Because choices are also not choices if the correct one is obvious. I also still think that grinding Aletta up when you want to be with her is a natural decision, even if somewhat time gated, we're talking 10 LP with a character you normally see every (game) day. It may be a bit abrupt, it needn't be this way, but I wouldn't call it bad design and not comparable to your "Ring of Plot Immunity Towards Sudden Dragon Appearances". I see it more akin to what happens in Mass Effect 2 before the suicide mission: you need to hurry, you don't know how much, and it may lead to a partially bad outcome if you don't. Happens, reload save and do it better.
It should of course be in line with the general setting. Another game on here (no shaming) will basically lock you out of a good ending if you order wrongly at a restaurant. And no, it's not "this is the girl's favorite dish" or some aphrodisiacum, just random and not suited to anything I can discern. That's obviously BS. But trying to get on the good side of a girl you want to be on the good side of - that works for me.
I think it boils down to this
A game should be fun. If I wanted to punish myself I'd play Dark Souls and not a porn VN.
Don't get me wrong, I like me some easy VN meal just like the next guy. On this forum at least. But if a game offers some gameplay, and yes, that can include grinding and failing at missions, I am not averse. Even if it is a porn/adult game, I prefer to be able to influence (and that includes influence badly, choices need to be meaningful) what happens to a kinetic novel. And that as somebody who absolutely dislikes Dark Souls because I consider it too punishing.
As for the second part, apart from Alexis Sasha and Cassidy also talk back to you if you refuse the NTR/threesome. To a lesser extend, you lose LP if you don't support polygamy with Anna and Aletta in their random conversations.
Well, the girls have one idea of what should happen, you have another, in the end you'll win out. To me the dialogue isn't overly passive aggressive but more that they don't just say "yes master, you are right master" but happen to have their own views and voice them. Even if in the end we all (well, most of us) will have 100 KP and collars on most girls, they should be allowed some leeway during the process.