One great fanfic could be 'A New Bond'. It really delves into the relationship between Dimitri and Byleth. It shows how they support each other during battles and in the political intrigue within the game's world. The author does an excellent job of portraying their growing feelings for each other in a very natural way.
The main reason is the complex characters. Dimitri has a troubled past and Byleth is a unique character with their own charm. Their relationship has a lot of potential for development. In the game, there are already some hints of a connection, and fanfic writers can expand on that.
One reason could be the complex plot that may be hard to follow for some players. There are multiple routes and a large number of characters with their own backstories, and it can get jumbled up.
It depends on personal preferences. Some might think the Blue Lions' story is the best for its focus on honor and loyalty. Others might prefer the Golden Deer's story for its strategic elements.
The story of Fire Emblem Three Houses can take a significant amount of time to complete, depending on your playstyle and how much you explore. Roughly, it could take around 50 to 80 hours.
Well, the Blue Lions' story is really engaging. It focuses a lot on the bonds between the characters. Dimitri's personal journey from a tormented soul to a strong leader is a central part of it. There are also many emotional moments among the group members, and the story ties in well with the history and traditions of the Faerghus Kingdom.