This is a large oversimplification. Just a glance at the verb section of the Bahasa wiki shows a system rich and nuanced in its own way. Sure, it does not fit the mold of a Standard Average European language, but that is no reason to knock it as having ‘no grammar’. A last note, Bahasa Indonesia has a mainland Asian counterpart: Malay.

https://en.wikipedia.org/wiki/Indonesian_language#Verbs

https://en.wikipedia.org/wiki/Austronesian_languages#Major_languages