My reaction to _Twin Eclipse_ was very similar, Tlaero, particularly to your point about storytelling momentum and retaining reader attention (in your spoiler).
Twin Eclipse is great, but it's biggest issue is retaining player interest until the plot takes a turn. I played through the first 1.5 acts in a sort of relaxed, semi-meditative state... primarily because I enjoyed the art and because I was (slightly) curious about where Arisushi was going... not because I found the story particularly compelling.
When the turn finally came, I _was_ hooked. But will most players stay engaged long enough for the story to gain momentum?
It's similar to my complaint about noping's first game, _Alive_. He (the dev) has a brilliant plot twist in mind, and understood the MCs backstory and reasons for his (disengaged, floating) behaviour... but we (the players) do not. So a player must be extremely patient until the plot reveals itself. I don't think most players are that patient.
Hooking players from the beginning strikes me as essential, particularly in story-first games that don't rely on porn. One of the best recent examples I can think of is _Shards of the Past_. Garou dumps the player right in the middle of a propulsive scene, which grips us _immediately_. There was no need for excessive exposition or introduction... we learn a great deal about the MC and the NPCs right away in a rather naturalistic way, as they react to events.
Let me be clear: I enjoyed Arisushi's new game a great deal. But... I wonder if the way it opens might deter some players.
You know it's funny. I've heard this before (from you, and others) but never really thought about it this way... I guess, in the perspective of a player. While I always sort of understood the point, I couldn't help but look at things from the perspective of an omniscient writer - as opposed to that of a player who lacks all the information.
For some reason the way you said this, really did make a few things "click" - which I think (among other reasons, certainly not the only) is one of the reasons the beginning of NSL is being received much better - that "hook" exists, and it comes very early.
It made me now think back to a number of games I've tried in the past - some of which have been extremely well received, and how I just never got into them. Many of them suffered the same problem - they lacked anything in the story to "draw you in" early, and instead relied on playing the long game. Many of them also attempted to make up for this by having the sex show up early and often - if they couldn't keep players invested early on with the story, they'd instead try with sex.
Ultimately it's not surprising in a field where almost every writer is an amateur, which tbf I think makes the well-written stuff all the more impressive.
It also ties in to something I've been thinking about a lot lately - the concept of an elevator pitch. Keeping things succinct is something I've always struggled with - any attempt to explain my thoughts has always been overly verbose - so I've thought about it a lot. For example, if I were to write an elevator pitch for NSL, what would it be? (Spoiler alert - I still haven't come up with something short enough to qualify.) Thinking about it in those terms though, I think has helped me with crafting the overall storyline. While I still might not be able to describe the game accurately in 50 words or less, I have made an effort to try to craft the "core" of the storylines in that mold, and then build around it - obviously you'd be a much better judge of it than me, but I feel like that approach has helped the writing for this game a decent bit.
I think devs in general would benefit from using a similar approach at times - since we really do have so little time to convince a player to keep going. Rather than writing our ideas, and building stories from them - at some point in the process, try to be as reductive as possible to our ideas, and then grow outwards. We exist in a space where sex and story are really the only 2 ways we have to grab someone immediately (One could argue art, but I know a couple of games with absolutely stunning art that have done poorly recently because they fail at the other 2) - and if we don't want to go all in on the sex, we have to make sure we're grabbing people with the story.
Then again, just like all but a small handful of people in this field, I to am just an amateur, so what do I know, really?