Not every devil’s strength comes from how much damage they can physically cause, it often ties directly to their concept and how fear of that concept manifests. For example, the Gun Devil is clearly a destructive force because it represents firearms and mass violence. Its abilities make sense because it’s tied to the fear of guns and their catastrophic potential. But not every devil is built for that same kind of large, scale destruction and that doesn’t mean they’re weaker in terms of AP.
Take Primal Devils, like the Darkness Devil (specifically). It doesn’t have any massive destruction feats to its name, yet it’s clearly portrayed as stronger than the Gun Devil. Why? Because it represents the instinctive fear of darkness, which goes beyond physical destruction. Its strength relies on its concept, and that’s where its power lies primarily as such for every Devil. The same can be said for Makima, who represents Conquest. Her abilities don’t revolve around mass destruction but rather dominating/controlling others. That kind of concept doesn’t need raw destructive power to be terrifying.
You mentioned that the Gun Devil’s threat was more widely known among civilians compared to Makima’s influence. Sure, the Gun Devil’s destruction was immediate and visible regarding that it wiped out 1.3 million people in five mins. But Makima’s power which is the fear of control isn’t about destruction as ive said earlier, it’s about the dread of losing your freedom, of being dominated by something you can’t fight back against. That kind of fear is harder to measure, but it’s powerful nonetheless. It’s the same reason the Primal Devils are stronger, they embody fears that are harder to define but instinctively felt in the day to day lives of humans.
Ultimately tho, not every devil is meant to be compared based on how much damage they can physically do. The Gun Devil is a weapon of mass destruction, but devils like Makima, Santa Claus or the DD operate on completely different. Their power isn’t about DC, it’s about how their abilities reflect their concepts. Scaling them fairly means taking this into account instead of just focusing on raw feats. The narrative makes it clear that strength is as much about the specific concept and how much it is feared.
Hence they should still scale regardless, primarily because of fear scaling.
Edit: Hence x2, the very existence of Devils should be constantly powering up Makima.