Are Sumatra or Sulawesi worth visiting beyond Bali and Java?
Yes, for travellers with time and appetite for rougher logistics. Sumatra and Sulawesi can make Indonesia feel bigger, wilder and less packaged, but they are not efficient checklist extensions.
Answer
Sumatra and Sulawesi are where Indonesia can become less polished and more rewarding for the right traveller. Sumatra might mean rainforest, orangutan country, lakes, long roads and a slower tolerance for distance. Sulawesi can mean culture, mountains, diving and routes that need more patience than a Bali–Java plan. These regions are not the obvious first choice for someone trying to “do Indonesia” in two weeks. They are for travellers who want the country to feel larger, stranger and less packaged, and who accept that logistics are part of the price. Add them when time is on your side, not when the map has a blank corner.