I mean, unless the game is horribly fucked balance wise, there always is some fun wiggle room in the viable build space. You can be creative/fun and viable at the same time. There are also meme builds that may only perform less than 50% of the time, but are extremely effective and fun when they do. Genuine fun despite general competitive unviability. It can also be fun to pursue your own optimization, without paying heed to the community distilled meta.
In conclusion, Mimi is suffering from a massive skill issue or the game is fucking horrible.