I feel your first point exactly. I made the mistake of choosing a Sky-only route for my first playthrough, as in I got absolutely zero points with the other girls. This meant I only unlocked 4 scenes, 2 of which were exactly the same, just with a minor clothing difference; and all of which were put in the beginning on the game. So I went through 90% of the game without any explicit content whatsoever, no lewd scenes, and without pursuing any other routes. And yet, despite this fact, the hours went by like nothing, and I stayed genuinely invested, without a hint of boredom or tiredness, until the end. No fatigue whatsoever.
I absolutely love Eternum, and Caribdis is an excellent developer. But what I just described is something that is only possible with My Bully is My Lover. Not even Eternum would be able to keep me playing it for 6 hours straight, without any lewd scenes whatsoever. Only this game could do that.