Honestly, I think everything you said is fair.
I can see why the route feels too fast. The main issue is that the game has a lot of characters, a lot of routes, and a lot of choices, and at some point I have to decide where to spend my limited development time.
If I made the Himawari NTR route a very long, slow-burn progression with many scenes, conflicts, and interactions over time, I would feel the need to give a similar level of development to her Love and Desire routes as well. And Himawari is already one of the most complicated characters in the game because she has Dom/Sub + NTR/Love/Desire, which creates a huge number of variations to support. So yes, the tradeoff is real: more choices usually means less depth per route, while very deep routes usually mean fewer choices overall.
I don't want to keep expanding the scope forever and end up dragging the game for many years. My current goal is to fully finish the game(or at least most of it) within roughly 12 months (also: no promises, but that's the target I'm aiming for). Extra content, side scenes, and additional events can always be added later.
And honestly, for my next game, I'm maybe thinking of reducing the scope overall. Fewer characters but deeper storylines is something I'm seriously considering. But at the same time, I really enjoy having a large cast to play with, so I'll have to find a better balance in the future I guess...
Thanks for taking the time to write such a detailed and respectful critique.🙏