Quoting from the article: "millennials with no hope of buying real estate, much less retiring, without stringent saving tactics, as well as families who need to downsize because of lost jobs or divorce."
These are people living beyond their means because they've no concept of the possibility that the future will ever present a worse situation than the present. Borrow, borrow, borrow and damn the future. What are consequences?
"stringent savings strategies" seems to be mentioned almost as an acceptance of failure of your life rather than a requirement of society. Having to downsize due to losing a job or divorce? Minimalism isn't going to save you from that, and neither, necessarily is a stringent savings strategy. Do they not expect any negative effects from losing a job or getting a divorce? Who are these people?
It's great that more people are being exposed to alternatives to 'buy everything so I can photograph myself in front of my extravagance', as a few people may be able to change their lifestyles. But wait a couple of years for articles about 'the failure of minimalism' because it was too hard for the average person / family to cope with. Such is the current culture of entitlement - with not much hope of improvement under Trump, the embodiment of entitlement. But post-Trump, there could be millions of reality checks in the mail.
It's completely up to you what level you want to engage with the material — maybe a student reads the blog post because they want to save money, maybe an adult buys the book because they want to get the information more efficiently and save time, maybe a company hires the seminar to disseminate the information to dozens or hundreds of employees, or an individual attends because they want specific advice to their situation, maybe an executive or passionate follower does the retreat to connect with the founders on a more philosophical level and get a very personalized experience.
From what I can tell, they are doing the same thing as Mr. Money Mustache but on a much more public stage and without the focus on early retirement/financial independence. Good for them!