Saying that Star Wars is too centered on Tatooine is like asking why books about World War 1 and World War 2 keep talking about Germany.
Is it? It plays a big role in ANH and TPM, but it’s very arguable whether the movies were actually centered around Tatooine - at least TPM - cause Naboo and the space/Death Star settings mogged Tatooine in both of them. None of the other movies were centered around it. In fact, the best prequel (ROTS) and the best original (ESB) had the least to do with it, so maybe it’s time to take a hint.
ESB is not the best original! They’re all tied.