And how does that manifest in civ7 to justify a full time historian? Civ is a history adjacent sandbox game - not historical and never was.
GAMA - the Game Manufacturer's Association, the 'trade organization' for all things gaming - disagrees with your views completely.
For over 10 years, at their convention ORIGINS, they ran a 'War College' of lectures and events all concerning the 'real' history behind games: lectures by university professors adn published experts in various fields, mostly military history because games are, at their base, all about conflict of some kind.
I was one of those lecturers, presenting 4 or more 1 hour lectures and occasionally participating in discussion sessions on various military history topics. The entire College usually produced 24 - 30 lectures or events, and attendance at each varied from 25 to 60 or more. Given the relatively small lecture rooms we got (the big ones all went to participation games and tournaments, of course) Standing Room Only was not unusual. As a percentage, they estimated that attendance at the War College involved up to 10% of the total convention, which given that ORIGINS was a major chance to try out new card, role playing, board, miniatures, or computer games which are, I should think, the primary interest of Gamers, that's not too bad.
And as to 'history not changing', that is specifically true only of historical events - they don't change, because they already happened. But our knowledge of what happened, why, when, and with what consequences, changes constantly. And therefore what kind of game we can/should make out of historical events can/should also change.
As a recent example, the domestication of the Horse has just been pushed forward about 2000 years and the 'history' of all early wheeled vehicles changed dramatically because for almost 2000 years after the first solid wheels those vehicles were pulled by oxen, donkeys, or equid hybrids, not horses. This is largely archeological rather than historical, but in game terms, it means that the consequences of The Wheel as a technology are utterly different from what the games have all modeled so far, and Horse Domestication does not mean Horseback Riding, it means Chariots.
The 'history' or event may not have changed, but the consequences of our knowledge change is very real if we plan to make a non-Fantasy game out of it.
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