Totally agree about the threesome thing. I'm not a fan of threesomes that just happen and don't make narrative sense. All three participants need to have been building that kind of relationship.
But for one-on-one scenes, I can see why there would be a sparse amount of content in the first half of the game. I love the slow burn, building relationships kind of thing. However, I've seen that sometimes culminate into an end result of very few scenes, with most being teasing and only 1, maybe 2 scenes being actual sex. Especially in games where the sex scenes are simple without options to change angles or positions, this is not super satisfying.
Groups scenes aside, I'm hoping each main LI gets at least 3-4 total sex scenes, as in actual sex, in addition to the 1-2 scenes of teasing they all have. Especially characters like Nancy who literally says she is going to let herself go wild and fuck the MC 6 ways to Sunday. If the dev is really "motivated by the writing" and doesn't give Nancy more scenes, that's kind of hypocritical, no? Characters like Luna, on the other hand are more shy and romantic. It would be totally reasonable to only have like 1 or 2 more scenes with her, but those scenes would be more passionate/romantic and meaningful.
The biggest dev mistake I'm dreading is relationship backpedaling (Future scenes with characters who have gone all the way already reverting to scenes with just teasing with no payoff). I see this a lot when a dev attempts to appease those who want more scenes.