One possible reason could be a lack of time. Maybe Ash has become too busy with other aspects of life, like work or studies, and can't find the time to write fanfiction anymore.
It could be that in this fanfiction, Ash had some personal issues come up. For example, he might have received some bad news from his family back home that made him lose focus on training and eventually give it up. Another reason could be that he found a new passion or interest that diverted his attention away from training.
It might be that Ash has other priorities now. For example, real - life commitments such as work or study have taken up too much time, leaving no room for writing fanfic.
One possible plot could be that Ash discovers a new type of Pokemon egg that is not like the regular ones. He has to go through a special journey to hatch it, and in the process, it's described as if he is 'giving birth' to this new and unique Pokemon. He might face challenges like protecting the egg from other Pokemon or trainers who want to steal it.
Yes, there might be some fanfictions on this concept that are written in a family - friendly way. Some authors might create a story where Ash has a more metaphorical 'birth' of an idea or a new beginning in his pokemon journey, rather than a literal birth which would be biologically impossible in the context of the original Pokemon series.
Maybe the loss of a very dear Pokémon friend. If something bad happened to a Pokémon he was extremely close to, like it getting seriously injured or lost forever, it could be so devastating that he loses the will to continue his journey and thus gives up.
The fanfic community is quite large and diverse. While Ash giving up might be noticed, the community as a whole has a lot of resilience. There are always new stories being created by different people. But it could also serve as a reminder to the community to support its writers better, so that others don't feel the need to give up like Ash did.
After Ash gives up on Charizard, the story may shift towards the development of the Pokémon that were previously overshadowed by Charizard. The fanfiction might show how these Pokémon grow and become stronger in Charizard's absence. At the same time, the fate of Charizard itself could be a major plot point. It could be on its own journey, facing new challenges, and potentially evolving further without Ash. This could set up a future reunion between them that is full of drama and excitement.
His Pokémon would be very confused and sad. They are used to following Ash on his adventures and having him as their trainer. If he gives up, they might lose their purpose and direction.