All MF needs to be viable is for her W and R to be reworked to Physical Damage
Sure you could give her QoL buffs for her passive, W etc., but that doesn't address any of her real problems
AD scaling magic damage helps early but it makes any itemization she goes for mostly useless later, its fine if she was a poke oriented ADC like Ezreal, Kog'Maw or Corki but she isn't. She is akin to Lucian and Graves, both who happen to love Armor Penetration items and often rush them.