I'm already in my early 30s and my circumstances did not allow me to start investing in my 20s even if I had the knowledge. I won't get into it now but it wasn't possible then. So that means I can only start investing now. Assuming that you do follow the expected timeline, what does retirement mean? Spending money for when you're no longer able to work? That assumes that you actually own your own home and only need spending money + medical expenses. And how can you unless you've invested in your 20s plus have you seen the current real estate market(Australia)?

I'm not sure I have a specific point except to say that the math stops working unless you follow the exact path expected.