I am a 30 year old Millennial that actually loves avocado toast, but have only ever had it at home. I was first exposed to it in 2007 during a vacation in Acapulco. It's easy and not very expensive if you make it at home. It wouldn't happen very often, but I would not think twice about ordering it out for $19 as the article suggested the price, however, I have never seen it on a menu.
This is coming from a millennial who spends $1,600 to $2,500 a month on food (groceries/eating out) for two!
Like others mentioned, it is important to align your spending with what you value. I'm not a big fan or follower of the mass frugality movement, at least not at the extreme end. At the end of the day we all have to have some level of frugality in order to create the gap between income and spending that is used to build wealth.
But I like to call that relative frugality. I would much rather focus on the income side of the equation and figure out how to earn $200,000 a year and save 50%, then earning $40,000 and save 50% of my income. I tend to believe that focusing on income keeps me in a state of abundance, rather in a state of scarcity when every expense is under scrutiny.
My two cents!