Sid Meier's Civilization 7 developer breaks down the new leader mechanics, "it's one of the biggest changes we've made to the game and one of the scariest"
That is true, but sometimes technology advances and it gets difficult to get the older titles to play nice with newer hardware. That doesn't mean the gameplay needs to be completely changed up in the next iteration.
Their design process is 1/3 old stuff, 1/3 reworked stuff and 1/3 new stuff. The idea is that why should release a new game if it's just the same as the last one. This is actually a problem so often that there is a recurring meme within civ communities every new release