There is no "higher ups" that demand these things. Every team and project does their own decisions with their own creative control. I used to have the role of being boss of all projects, and having final creative say over everything at PDS until end of 2019, a role that Henrik Fåhraeus now has, and nobody micromanages a project in that detail.
Nowaways, most of the projects are created by people who used to be fans, and got hired to work for us, and they make ambitious new things.
Back in the day when we did a sequel.. Like HoI2 or Eu4, we took the previous game, added a few "big" features, upgraded the graphics a bit, changed some UI, and called it a sequel.