I respectfully disagree, for several reasons:
It is what you spend, not what you save, that determines what sort of income stream you're going to need to sustain yourself in retirement.
It is the amount you can save, not the rate at which you save it, that moves your retirement date forward (or backwards).
Consider someone slaving away earning minimum wage at McDonalds... even if it were possible for them to have a 50% savings rate the chances of them being able to retire early are pretty small because the amount they are able to save is pretty small.
Compare that to a doctor or IT person comfortably earning six figures. The amount they can save is much greater, so (ignoring lifestyle inflation for a second) it follows that they should be able to afford to retire at a much younger age.
This I do agree with.
If you think about it, traditionally many of the people you hear achieving financial independence at a young age were able to do so because they'd invested in real estate. Not because that asset class performs significantly better or because there is some land lording secret sauce, but because of the early use of leverage.
When it works the returns achieved look like those ubiquitous "magic of compound interest" post calculations on steroids.
I think this is certainly true.
The US market conditions over the last 10 years or so provided everyone with the same opportunities to benefit from that bull run, which has resulted in a lot of recent FIRE folk who were able to get there using index funds.
It feels like there are a lot more of them partly because of the PF bubble we live in, and partly because social media makes it much easier for them to gain a following and be noticed quickly (e.g. the rapid growth of the Millennial Revolution brand).
The formula for succeeding in personal finance is dead simple and well known. For example The Richest Man in Babylon was first published in 1926, and the lessons it taught are pretty much the same ones that get endlessly rehashed on all our blogs.