If you want to make a comparison, Greece did nothing to fix tax evasion.
And neither are we.
Tax evasion is not an easy problem to solve. Nor is a fair taxation system easy to develop.
The GST is one that corporations have some difficulty dodging on the revenue side, but independent tradies don't, because they can decide to only work for cash as many up here do. However, an increased GST gets those cash workers when they spend at least, but an increased GST rate would come down more heavily on the everyday person. By contrast, income tax and turnover tax is something corporations can duck by distributing income between their subsidiaries here and overseas and choosing in which section to declare the profits - at their manufacturing site in, say, Thailand, their sales point, say, here , and their shipping line based in, for example, the Caymans or Liberia, but higher income tax levels may hit the middle wage earner harder.
I'd personally favour and income tax with a higher tax free threshold and a steeper rise at the very high end, but that is difficult to balnce correctly too. In principal a super-tax on incomes over $300,000 per annum and a super-super-tax on those on 7 figure salaries and bonuses may look good, but I'm sure there would be holes in any plan to do that too.
We also don't want to tax big businesses so much it encourages them to leave the country entirely.
And I recall the time when Paul Keating had a shot at stopping negative gearing on rental properties and had to back down when a shortage of rental properties developed and rents rose rapidly.
SO were do we go??
Certainly not to spending the money anyway and gambling on it all working out, and/or to relying on finding a magic way to raise more revenue preferably from "them" not "us".