I'm not sure if you're aware but the places where the rail lines (the coasts) are pretty much 80% of the Australian population. Australian rail is... not the greatest, but there is rail where people actually live.
Last time I went home I bought a 3 month NSW regional rail pass, which will also get you to Brisbane and Melbourne.
Nearly 70% of my booked trips were replaced with buses. One from Sydney to Canberra ended up being 7 hours long, the train takes 3. Pretty disappointing.
High Speed rail has been discussed for decades now, huge studies and inquiries, the route is basically decided, but it was always deemed "too expensive". Note that we spent 3x the cost of a 10 year Melbourne to Brisbane HSR system in 2021 on covid cash handouts.