Someone might think this because if they are new to fanfiction or only really follow a particular subset of fanfiction related to Izuku Midoriya. For instance, if they mainly read stories from a specific website or group of writers who focus a great deal on Izuku Midoriya, they may not be exposed to the wider range of male heroes in fanfiction. Also, if a person is really attached to Izuku Midoriya's character arc and story, they might subconsciously assume he is the only male hero in fanfiction without realizing the vastness of the fanfiction world.
Yes, there are. However, their availability might vary depending on your location and the specific comic publishers. Sometimes, limited editions or special releases of All Might comics can be harder to come by.
Definitely not. Midoriya's character is very much alive in the manga. The creators have no intention of killing him off as he's a key figure in driving the narrative forward and inspiring other characters.
It adds a new dimension to the fandom. By focusing on a little girl's relationship with All Might, it can attract a wider range of fans, including those who like stories with a more emotional and nurturing aspect. It can also inspire fanart and other fan creations related to this unique relationship.