Oooof, ok I'm weighing in on this one, because as a millennial Australian brunch-loving non-homeowner it is right in my wheelhouse.
Firstly, I think all mustachians agree that frivolous expenses like brunch and daily takeaway coffees are exactly that: frivolous. It adds up and eats into your budget and most people my age seem to consider it a necessity (even though there's free coffee at work, that's what really confuses me). So yes, live within your means, save half your income, invest the rest. Simple.
However, the whole Australian trend of "Millennials are useless because they all have iPhones and don't have houses like me" articles is getting a little tiresome. It's pretty hard to make a comparison between Australia and the US in this regard. We have a teensy population, and it's concentrated along the coast and especially in Sydney and Melbourne. While the US has equally massive cities with crazy housing costs, there are also a ton of smaller cities that are going through a renaissance in terms of appeal to younger people. In short, there's choice. Australia lacks that geographic diversity. That said, I live in a small town in Canada now, and the lifestyle definitely appeals to me. When I move back I would certainly consider somewhere outside the major cities, mostly due to affordability.
This specific issue of the smashed avocado came up last year by an angry boomer columnist who is probably seething that his article didn't make the international press. Many excellent rebuttals were made then, this is perhaps the best summary:
https://www.theguardian.com/business/grogonomics/2016/oct/18/i-could-get-outraged-by-this-boomer-millennial-war-but-id-rather-look-at-the-evidenceI also really enjoyed this article (published 2017) about millennials buying property in Auckland, which is going through a similar housing price boom to Sydney and Melbourne. A deeper dive into these stories reveals they are out of date, rely on large gifts from family to get started, etc.
https://thespinoff.co.nz/media/20-04-2017/how-to-buy-your-first-house-a-deep-data-dive-into-those-miracle-property-stories/In short, the vast majority of every generation doesn't live within their means. In some situations you can still afford a house without too much financial duress. In other markets buying a house could take years of saving and young, mobile people aren't willing to make that sacrifice. Should they be throwing their money in index funds instead? Absolutely! But that fault sadly spans all generations, across all socioeconomic strata.
(As a complete side note, one of my favourite pastimes at the moment is scanning the local real estate offerings in this tiny, economically depressed Ontario town. From an Australian perspective, it's a hoot! "A four-bed, two-bath house for $165K?!? OOoooh a three-bed, two-bath house for $98K!" Sadly as a temporary citizen a mortgage is out of the question, my SO is not sold on property, and I don't quiiiiite have the cash on hand just yet.)