I played Indonesia on immortal, few days ago, and won through
scientific victory (first victory, and second game in BNW), ahead of France and their expected cultural Victory, around turn 370 (somewhere around 1950s)
I played a random map and got continents. On the whole map there were two continents and only two one hexagon tiles (islands) to acquire all unique resources (nutmeg, cloves and pepper). I played long time with two cities, at some time got a third one, and settled fourth just before the end (it is surprise that city spamming AI did not settle there sooner. I kept it safe in some shorter period with a unit, though). I settled the last one just to see what is the last luxury resource
I had great relationship with everybody, held first World Congress, built Porcelain Tower, declared friendship with literally every other civ, finished rationalism, and have been doing research agreements constantly until last 35 turns (by that time I was far ahead, finished Hubble, and produced numerous scientists which boosted final science leap themselves). To be in great relationship, I suffered by proposing arts funding resolution and similar non beneficial ones, and France was very close due to that, but I managed not to be annihilated by their 10 times bigger army. At one point I was delayed in Science victory, when few AIs were plotting against me, so I had to pump military (advanced but small in numbers) to avoid being attacked. It made a significant drawback, but at the end I think I managed to beat France by some 10 turns or more...
I can say that if you play diplomacy well, you can benefit from new resources, trade them well, and then you are most prone to win
diplomatic or scientific victory. I did not manage to match France in cultural/ tourism sense. I have not resisted their tourism influence, although I had Hermitage, museums, opera houses, around 8 Wonders etc. France was in my game cultural superpower and I won, because they have not influenced lone Hiawatha on another continent. I would say
cultural victory is toughest of four, for Indonesia.
Domination is also, in my opinion a tough choice for them. UU does not seem strong enough, there are much stronger units available, so in my opinion go towards
Diplomatic or Scientific victory.
If you go through liberty and piety trees and manage to build a lot of cities, their Unique Building can help a lot. Than again, I would say that would be more beneficial for keeping you happy/ rich, giving you more possibilities for befriending city states and once again push you in direction of Diplomatic victory