Hello there, Webnovel moved the old fanfics genre which was under "Original Novels" into a brand new category, and officially named it Fanfic at the top. Fanfic genre currently has a few subcategories. You can get all those stories by updating your app to the latest version. (We haven't 100% released it to everyone yet)
In addition, fanfic needs authors to fill in a few basic info in advance if writers would like to publish new chapters. It requires author to add Topic/Theme of the title. Authors can also indicate characters of the story now. Later on, readers can search through characters and theme topics to get the right title for their entertainment.
However, there are over tens of thousands of fanfics still missing these info (because the old system never asked the authors to provide them, and isn't the fault of the authors). At this stage, all uncategorized titles (which means missing either subcategory under fanfic or no theme) will be arranged into "Other" until authors put all required info.
Aside from that, in the translation field, there were some CN novels which are considered relatives to ACG (animation, comic, game), they will be still staying in the ACG genre.