Now that I've had a chance to play this, I agree with those who said it feels half-baked once you start poking your fingers in. Since there's no way to engage with any lewdness other than intentionally losing and occasionally seeing a bad end pop up, the lewdness/submissiveness mechanics don't even have a reason to be in the game. While I can't speak to how satisfying the NTR is or isn't from the perspective of a fan - as divisive as it is I'm one of those rare people who don't have a strong reaction either way - to me it came off as totally boring for the "pure" romance to stop if you engage with the NTR aspect. In my mind the whole point should be the girl struggling between her love for totally-not-P3-guy and trying to navigate dangerous situations where a mix of carnal desire and aggressive personalities either make cheating on him seem tempting or come across as the only safe way out.
From what I read of them they made heavy use of hypnosis, too, and I find that extra boring for this angle. Maybe as pure degradation or corruption or whatever you want to call it, but cheating isn't interesting if someone's been hypnotized to do it.
In one of these posts (or maybe one of the reviews) someone mentioned that the rival character completely took them out of it because he's just a god mode wiener and I'm leaning in that direction, too. As part of the story it was somewhat interesting for him to so clearly be involved yet stay just far enough out of reach that the team couldn't pin anything on him, but if you get the good ending this doesn't get resolved. As far as the h-material goes, though, he is literally a skinny guy whose head has been pasted onto the physical embodiment of porn cliches. The Rikka NTR route is the only one that really puts the effort in; even there, though, she's just powerless to do anything other than dance to his tune. There's no finesse or struggle to it.
All of this could be forgivable if the core experience was pulled off well, but that brings me to by far the most underbaked aspect: the MC's lewd development. On paper it could be hot for the missions to carry an element of danger for him, too. There's room to play with the pieces for different scenarios, like the girls staying pure and P3 guy getting sluttier which leads to some NTR, the girls gaining lewdness while he doesn't and feels those helpless NTR feelings, or both of them developing alongside each other and desperately trying to hold on to their feelings for each other all the while, but all we really get are a few game over scenarios where he also gets raped and one danger scenario for him that you have to trigger all the NTR routes in order to complete - and then there's no proper 'NTR route' for him. What's the point if the characters and the story don't acknowledge it and all the scenes that use it are bad ends that don't require any sort of development to reach?
Some of the out-there bad ends were weird enough to catch my attention, at least. That's part of what we're expecting from a Marimo game. It's just a shame that they all come across as disconnected one-off ideas to look at in the recollection room rather than fully realized scenarios that you'd come across and need to navigate in the actual game.