The possible reasons are many. Firstly, the fanfic might not be in line with the official Pokémon storyline that Ash is accustomed to. His character development and relationship with Misty are important aspects in the official story. If the fanfic distorts these elements, he would reject it. Secondly, the writing style of the fanfic could be off - putting. If it's too convoluted or hard to understand, Ash (as a character in this context) would not be interested. Thirdly, if the fanfic focuses too much on a romantic aspect between Ash and Misty in a way that Ash doesn't feel comfortable with, given his more friendship - and - adventure - oriented personality in the official story, he would reject it.
One reason could be that the fanfic has a strange or unappealing plot. For example, if it makes Ash do something completely out of his character, like being mean to Misty for no good reason.
Maybe the fanfic contains inaccuracies about the Pokémon world that Ash is a part of. If it misrepresents the relationship between him and Misty in a way that he doesn't like, he would reject it. Also, if the fanfic has a very dark or inappropriate tone that doesn't fit with Ash's positive and adventurous image, he would not be on board with it.
Chapter 190, "Xia Li, 4 Articles, Someone is Coming", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Upon hearing this question, a peculiar expression appeared on Xia... to As the wedding proceeds as planned, others in the camp will surely....
Chapter 225, "Council at Long Mountain, the Decisive Li Xuanling", is the clearest early answer because it turns Yu Bin's situation into a concrete plot event. The chapter gives readers a real answer by opening on While Xia Hong was busy disguising himself as Hong Yu and prying... and ending on Second Uncle, Yu Bin and his companions not dying is a reality..
Chapter 260, "Medicine Workshop Upgrade, Population Surge, and Resource Easing", is the clearest early answer because the rescue effort creates visible on-page results. Early on, From April 29 to May 9, the massive population migration finally.... By the end, From the perspectives of Cold Beasts, vegetation, herbs, and....
Chapter 274, "Weakness and Power, the Final Battle Begins", is the clearest early answer because the buildup finally cashes out in a real clash. A useful checkpoint is the way the scene starts with On the outskirts of Redwood Ridge, a five-hundred-meter square area... and follows through with This disparity in strength is truly too great!" Even though he knew....
Chapter 256, "Yuwen Dao's Suspicion and the Jade Bone Medicine", is the clearest early answer because the rescue effort creates visible on-page results. The chapter gives readers a real answer by opening on Greetings, leader!" Soon, Luo Yuan led Yuwen Dao and Yuan Cheng in... and ending on On the night of April 27, before the appearance of the White Dew Gu....
Chapter 298, "Hou Jing Surrenders, White Abyss Falls, Zhaoyang Changes Its Flag", is the clearest early answer because it turns Great Xia's situation into a concrete plot event. The setup is Hou Kong is twenty-six this year, has a Superior Battle Body, and his..., but the pressure keeps building through Unfortunately, even Hou Hu back then was nothing more." On the....
Chapter 196, "Sword Puppet, the First Intermediate Squad", is the clearest early answer because it turns Thunder Kui's situation into a concrete plot event. The chapter gives readers a real answer by opening on Qiu Peng knew this very well, so the target of his broad knife could... and ending on From within the piled snow, a crimson giant lying flat suddenly sat....
Chapter 201, "Wuyuan Garrison, Cold Marrow Iron", is the clearest early answer because the buildup finally cashes out in a real clash. It opens with Because as he spoke, he was constantly observing the reaction of that... and closes on Yes, hadn't the Great Xia Leader just said he knew his father?.
Chapter 306, "Helplessness, Shifting Loyalties, Total Annihilation and New Territory (Part 2)", is the clearest early answer because it turns Cold Resistance Level's situation into a concrete plot event. The chapter turns that into something concrete by moving from All right, listen to the leader and go ahead to keep watch!" Although... to The boy is simply too young, too cautious, afraid of everything..
Chapter 186, "White Bear, Mountain River Team, Stranger", is the clearest early answer because it turns Yue Feng's situation into a concrete plot event. The chapter turns that into something concrete by moving from Li Yuankun was the first to recover. to But Yue Feng was still not reassured, worried about other teams....