I wouldn’t say so. Colonisation has a deep and lasting impact on our cultures of course, but to say that none of the precolonial customs were maintained is a bit of a stretch.

It is more accurate to describe Nusantara, or the Malay archipelago, to that of South Asia. Native languages are still spoken. Cultural traditions have largely been maintained. Although, there is now a confluence of Westernised middle classes, reactionary traditionalists and chauvinists, isolated indigenous groups, and accompanying capitalist classes and imperialism attacking collectivist values and structures in our societies.

Just to raise a few points about it, for religion, christianity missionaries did penetrate the southeast Asian archipelago, with the most obvious example being the Phillipines, having a christian majority, but in the case of Malaysia and Indonesia, it had a very limited impact on indigenous religions, most importantly being Islam, Hinduism, and local traditional faiths, however christianity gains prominence the more eastwards you go.

Western Papua and Sarawak (East Malaysia) has christian majorities for example.

Language is another contentious issue, with both left-wing and right-wingers in Malaysia for example, supporting the use of Bahasa Melayu (Malay) as the main language of the government prior to independence. Again this has some exceptions, with for example Sarawak, maintaining English as the de facto language of (state) government even though Malay is the national language.

Indonesia has only bahasa Indonesia as their national language, but other indigenous languages are recognized in the regional level. I can’t say for sure about the specificities of Indonesia’s national language policy, but from what I know, “colonial” languages like Portuguese, English and Dutch have a negligible amount of speakers or relevance there.