That is sort of like saying money doesn't buy happiness...true, but financial stress or poverty typically can be outright bars to happiness. As you say YC admission or raising funds from investors isn't a measure of business success...but then again I haven't seen a tech unicorn that hasn't been funded by investors.
>Head down, work, balanced lifestyle, try to make something small succeed on your own.
That is a great message to tell to the 99% that get rejected from YC and will never touch VC funding...but even that sounds more like a pipe dream than the American dream now a days.