I've lived overseas and I disagree.
Australia is no more racist than some other developed and developing nations, and there are countries with more racism than Australia.
Travel to different cities in the US and notice how neighbourhoods are subtlety segregated by race.
Talk to any European about their thoughts on gypsies.
Ask Japanese about their thoughts on Koreans.
Look up the usage of the word "keling" in south east asian cultures.

What we have in Australia is perhaps a more overt style of referring to cultures or differences, but the barriers to integrate with Australian culture is much lower than other countries. For some migrants that have come from cultures where they had a racial privilege (e.g. caste systems), it could now be confronting to them that their standing in Australia is lowered and equalised.

The way that we establish social bonds (banter, joking around, jabs, insults etc) can also be confusing to foreigners and be perceived as racist, but it's an old UK way of establishing camaraderie by proving that you can dish out an insult but also take it as well. Like stand-up comedy material, this method is being tamed as time goes on.

One final indicator of racial division is the level of mixed marriages. If it was a serious problem, we would see low levels of marriages between different countries of origin. In the EU, the rate of mixed marriages is about 8% (1 in 12). In Australia, the rate is 3.5x larger at 29%.

I wouldn't necessarily phrase it like that. There's a danger of oversimplifying the problem into just good (non-racist) and bad (racist) people and that doesn't help at all. The problems are systemic and go right to the very core of our nation. Non-Indigenous Australians will continue to make irrational, selfish decisions with regards to Indigenous Australians for as long as they don't understand why Indigenous culture is important (not just in Australia, but throughout the world) or the truth of their nation's history. Australia is culturally uneducated and unaware compared to the rest of the world and that has to change for any further progress to be made with regards to recognising Indigenous sovereignty in some form.

anyone who has lived in any other culture and then returned will agree

Big call. I've spent a few years south east asia. Racism and classism is deeply rooted in their cultural psyche. As a European foreigner you're the beneficiary of their preconceptions, but talk to pretty much any of them about neighbouring countries, or differing religions and you see a very different picture.

Yeah, I've mentioned to some friends and family that my wife and I are moving overseas. I don't use Facebook or anything, I've purposely not engaged in discussions with them about the Voice.

And some of the hate and vitriol has been astounding. Full mask-off Aussie exceptionalism.

The Voice was just the nail in the coffin for us. We'd been considering moving for a while. I wish Aussies really knew how fucked our work culture is. And how shit our pay is relative to the cost of living.

They're living in a fantastical version of Australia sold to them by a nationalist media.

Yes, 1000x yes. Lived there for 18 years, have lived in two other countries so have good reference points. I love Australia, I love Australians. But en masse some disturbing trends come out.