We definitely do need denser housing in the inner suburbs, but with the questionable build quality of post-2000 properties, we probably need a significant overhaul of building standards and requirements first and foremost.
Heating/cooling should not be so expensive and futile, given our relatively mild climate. Proper insulation, double/triple laminate glass, awnings over north & west-facing windows etc.
Additionally, many new developments are built and billed as ‘luxury’ - pricing out a lot of potential buyers, and builds rarely have the appropriate number of rooms for young families.
Lastly, accessibility concerns usually mean that new developments beyond 2 stories usually require an elevator - so in order to make the build cost effective, the designer ultimately needs to become 5-6 stories tall; infuriating NIMBYs who may otherwise tolerate a 3-4 storey tall build.
There are a lot of problems that need to be tackled, but they need to be tackled - both from a Federal (against financial incentives towards property hoarding and speculation), and State (building adequate levels of appropriate stock).