Gacha doujins TLDR for the newfags

Blue Archive
>easy to draw
>Nexon pays artists to draw doujins

Genshin/ZZZ/Honkai
>designs are hard to draw
>also all the doujins are yuri/yaoi

Nikke
>the japanese do not like asses
>also the few doujins they get are always about anal and ass worship

FGO
>literally dead franchise
>none remembers it so no doujins get made anymore
>kept alive by boomer whales

Everything else
>too small or irrelevant to make a dent