Champion Passive Reworks

I've been looking over passives from some older champions, and I realized much of what makes them too good/too bad is their passive. Nowadays, passives tend to add something interesting to a champion (Gnar) or fill in a weak spot on a champion (Lux's provides reliable damage that Lux doesn't have) and have EXTREMELY powerful effects that feel good to use (Braum, Jinx, Tahm) or even have a full kit built around it (Vel'Koz.)

But older champions passives are almost forgotten. I think you should have to think about your passive as much as your other abilities. Unfortunately, we have champions like Amumu, Kayle, Talon, Nunu, Leblanc. Many of these champions are also constantly problems. Much too weak, or much too strong.

We recently had a mana budget reevaluation based on ult power. Could we have the same, but for interesting gameplay on passives?

TL;DR: There are champions who I can be playing and literally forget they even have a passive.