I know very little about Australian finance, but in the countries I *am* more familiar with, people lacking in spare brainpower--as long as they are also lacking in Weird Tax Shit--can just walk into a bank and say "here is some money, tell me how to invest it".

They'll steer you towards higher-fee options, but those are almost certainly better than nothing, and you can change it later if/when you acquire enough spare brainpower to figure out what the local low-fee options are.