I think "cult of personality civ" is a matter of design rather than anything inherent.
Truth be told, I'm inclined to agree.
However, the way Firaxis has treated Civs in the past is telling of how they might treat them in the future. I concede that many of the examples I listed in the original post only tenuously fall under the category I described. Truth be told, Civ VI only had two true Cult of Personality Civs and they were Macedon and Gran Colombia. However, Firaxis was still interested in using many of those in my list as vehicles for their pop history traits. The Scythians were led by Tomyris (with her ability literally being a broad combat bonus called "Killer of Cyrus"), the Phoeneicians were led by Dido when real leaders were right there, and Sumer
was reduced to the Gilgamesh Civ.
We can discuss what should or shouldn't happen and what may or may not qualify, but that doesn't change the fact that Firaxis might see things differently.
I think we have reason for hope, though: 1) thanks to considerate historians like Andrew Johnson and the evident discussions that took place in the design and implementation of these new systems, and 2) Firaxis was steadily improving. Macedon was little more than a vehicle for Alexander in Civ VI, but that didn't stop Firaxis from taking a good shot at designing them fairly and accurately. Same goes for Gran Colombia. Even Civs that lie on the fringe of this Cult category (I feel that the Zulu are very much used as a Shaka shoe-in) were still given designs as separated from their Leaders as possible.
So whether or not some of these Civs get to remain (don't worry Zaarin, I firmly believe the Phoenicians are coming and fully deserve to come
) is definitely a question that Firaxis themselves was/is asking, and I hope they are coming to many of the same well-informed opinions found here.
And just to make it clear, I wrote my original post from the perspective of what
Firaxis might consider Cult of Personality Civs, or more broadly, Civs that are or are used as excuses to include a certain leader. I do realize it's impossibe to tell whether the decision to include Phoenicia (or Carthage as they were in Civ 5) came before or after the choice of featuring Dido as their leader, but the trend towards "big personality" Leaders led to a lot of choices that felt rather cheap, or more like a convenient coincidence than a good-faith "let's include this Civ this time around." If I remember correctly, Firaxis would design the Civs mechanically first and
then find a historical backing, only fine-tuning it to be truly Civ-specific after the connection was made, which perfectly explains that phenomenon. Thankfully, such a method seems dead and buried with the introduction of Civ-specific Great People and Civic Trees. The process has changed dramatically.
Perhaps I'm just internally confusing my distaste for the "big personality" motive with the topic at hand. If that's the case I apologize. I hope there was some value in this fanatical ramble. Let's keep the discussion going.