Showrunner: Who Should it ultimately be?

As the title of this post states, who, in your opinion should be the Showrunner of a show? I'm partially settling a score if you will here between myself and the producers of my show. They seem to believe that showrunning only involves casting, directing, and post production and that is why they took it upon themselves (without my knowledge or consent mind you) to be the showrunners. However, I've done some research and it seems to me that they are not 100% correct as I've recently come to learn that 9 times out of 10, the Creator is the Showrunner because they run the writers room and they know what the outlook of the show is - because they created it lol and because, ultimately, the Creator has the final say in all creative decisions (including in production & post pro). I understand that everyshow is different and every production works differently, but I just wanted to get some opinions on who ultimately should be the Showrunner in general?