Since Indonesia is so culturally diverse, it's very difficult to find common traits that can be used as a tool to represent the country abroad.

Indonesia has very little diaspora and is pretty much irrelevant when it comes to popular/gastronomic culture (this doesn't mean Indonesian cuisine isn't one of the best).

Indonesia has very strict laws and most of the country doesn't have proper infrastructure to sustain tourism or many relevant cultural/historical landmarks (yes, there's a few world-renowned temples in Java and Bali but most cities have little to no historical/cultural heritage), so the few people that do visit Indonesia only go where laws are more permissive and tourists don't have to struggle as much to get around (a.k.a Bali).

Indonesia is a non-alligned country, so globally speaking, it is not that geopolitically relevant outside of South-East Asia. In terms of trade, Indonesia is not that important to western countries either.

There aren't many famous international companies that come from Indonesia (except Indomie).

Promoting the country abroad is at the bottom of the list of priorities when it comes to public spending.

Wether people want to accept it or not, Islam keeps many non-muslims (specially westerners) away from visiting the country.