Maybe it's because in the story's context, accepting plushies might go against her character development or the specific narrative arc. It could be that her character is designed to have a certain view on physical items like plushies that doesn't align with acceptance.
One possible reason is that her new mindset in Monika After Story doesn't allow for such frivolous or sentimental items. She might be focused on more important or complex aspects of her existence and see plushies as a distraction.
As of now, the Genshin manga is not finished. The story is still evolving and there's more to come for fans to enjoy. The creators are taking their time to develop a rich and engaging narrative.
There's no definite answer yet. It might continue if there's enough demand and the creative team has more story to tell. But it could also stop if they feel they've completed the story arc.
There is a Genshin Impact manga available. It brings the game's world to life on the page with beautiful art and engaging storylines. It's a great companion to the game.