I don't quite understand. Where in Civ is there room for the in-depth, philosophical interpretation of history that you're alluding to?
The history in Civ is largely limited to two things: the skeleton framework of human history that guides the overall flow of the game, and the different historical facts that provide the window-dressing and flavor for the game's systems, mechanics, and factions. These things require no sort of esoteric knowledge, and there is practically nothing useful or interesting for us to observe about these things to the developers beyond "I just finished reading a Wikipedia article. The devs should add this" which is what 95% of fan ideas boil down to.
Reciting historical facts is the lowest hanging fruit for people to critique or comment on for historical games. It doesn't require in-depth thinking, it doesn't require reasoned consideration of how every other facet of the game is affected...it doesn't even require you to really play and understand the game. It's fun for people to talk about their pet subjects. It's absolutely no coincidence that the topic that generates the most discussion for Civ is "What civs do you want to see?"
But I'm much more interested in different ways to add to the core gameplay loop, or elegant solutions to entrenched problems the series has.
Well, "historical facts" might be the lowest hanging fruit, but that was not the basis for the criticism of the games I mentioned: Humankind, Old World, or Millennia. As I read the critical comments on those, they seemed to be based on Lack of Gamer Agency, Lack of Identification with the faction you were playing, and confusing game mechanics. That's probably incomplete, because I stopped reading anything about Humankind or Old World many months ago and haven't read anything about Millennia since the Demo.
But that said, I don't think we are entirely different in our views. By far the most important things in making a game both popular and playable are game mechanics and game-play in general that are clean, clear, and work to advance the stated objectives of the game ('Victory Conditions'). A huge bonus is game mechanics and game play that can advance in several different directions based on different objectives, which enhances Replay potential enormously.
The disagreement is in Emphasis: I happen to think that there are potential solutions, or ideas for solutions to problems in the core gameplay or entrenched problems in game mechanics in the Historical Database. Especially in a game that identifies itself as a historical 4X in all of its presentation: Leaders, Civs, Great People, Wonders, cities, named terrain, titles of Techs, Civic, Policies, etc - any Fantasy elements in any of those gets commented on almost immediately, because it goes against what gamers have been led to expect from the basic Civ game. And the more 'esoteric knowledge' available about that Database the better, even if no specific part of it makes its way into the game.
The examples I gave were trivial with regards to ordinary game play - they were designed to be more
outre than useful.
But for another example of Historical Detail that could effect an element of game design, the Ilkum (Ilka) policy in Civ VI, an Economic Policy, in-game relates to getting cheap Builders. Historically, this policy was present under the same name in Sumer, Babylon, Akkad, and Assyria. I still have to check the Mitanni and Hitittes, but it appears to have been generally in use in the Bronze Age Middle East. It was a form of Conscription, rounding up a percentage of the available manpower each year for either military or civil service - enlisted workers or soldiers. In other words, while immensely useful in gathering manpower for irrigation, Wonder-building and other Civic projects, it also provided a large force for the armies, mostly composed of spearmen and archers or slingers, but occasionally more impressive troops like chariotry.
Knowing that, as a Policy or Civic, Ilkum/Ilka could be used for cheap troops as well as 'free' or cheap Builders or major discounts on the 'currency' used to build Improvements or Wonders depending on the game design. It could also be the basis for a very early division of military Units into (cheap) Amateurs and (expensive) Professionals, since that was its real use in the historical civilizations. I don't think any Civ since Civ III has modeled any variables in Troop Cost, but if that is deemed necessary or worthwhile as a game mechanism, here's a historical effect that, from the very early game, can be used as a basis for a game mechanic to effect that.
Not a huge effect, but little effects Add Up, and it's far easier to start from something already used and developed to address some 'problem' than to try to make up a solution yourself.
To quote Master Kung, one of the three ways of acting wisely is Imitation, and it is the Easiest.