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.
The difference being that discussions of WWI and WWII have to include Germany. Star Wars films after 1977 do not. They do only because Lucas had writer’s block trying to pen any sort of story after the only film he had written or planned in the 1970s. He’s the one who has tied us, unfortunately, to The Solar System Far far Away.