In adapting Isaac Asimov’s Foundation to the screen, David Goyer changed the story a lot from the original book. I don’t have any issues with gender flipping characters like Gaal Dornick or Salvor Hardin. I don’t mind the addition of clone emperors (I actually rather like the Cleon story lines). I don’t even mind changing the details of Hari Seldon’s life and fate.
The issue I do have is the way that the changes undercut the fundamental premise of Foundation–that the tides of history are inevitable, and do not depend on the actions of individuals. Protagonists like Salvor Hardin and Hober Mallow do not succeed because of their midichlorian count or martial arts training. The win by recognizing the broad forces at work in civilization and acting accordingly.
In the books, Salvor Hardin is a canny political operator who outwits the Encyclopedists and Anacreonians, and lives by his maxim, “Violence is the last refuge of the incompetent.”
In the TV show, Salvor Hardin is a deadly sniper who kills dozens of enemy soldiers, and fights the villain in hand-to-hand combat. At one point, her mother says the famous line, “Violence is the last refuge of the incompetent,” only to be overruled by Hardin, who takes military command of Terminus.
Foundation is a book about ideas. Changing genders, adding more sex, and portraying a galaxy with many different skin tones is orthogonal to those ideas, and is appropriate for a modern adaptation. Those who object to these changes claim to be purists, but really just want to indulge their atavistic desire for the traditional virile white male hero who smites his enemies and seduces space babes of different hues (a description which fits characters ranging from Captain James T. Kirk to the original sci-fi hero John Carter–who was, I kid you not, a Confederate Civil War veteran).
Abandoning the core ideas of the book in favor of generic sci-fi action makes the show, in a paraphrase of Douglas Adams, almost, but not quite, entirely unlike the source material.