In all honesty, especially in this meta, I could see her passive not being set inactive upon damage at all. Most other ADCs have a repositioning tool that does not become inactive except when used (on CD). MF's passive still requires her to physically move to a new position. If her passive was never removed, she could move faster than all other ADCs, but other ADCs could still gap close whenever they needed to. This would, of course, require that Kog & Varus received some compensation for their lack of an escape/gap closer. Cait would also need an easier escape mechanism to pull off.