18/10 week, page-176

"If you invest in an index fund then you would certainly make decent returns over a 10 year period."

The issue with this statement is.. it's true.
When all the smart people just blindly buy the index funds, the underlying stock values become disconnected from fundamentals, we're seeing that now.
Nobody knows just how disconnected they could become. Once there's no relationship to fundamentals there will be nothing holding stocks back. Look at Gamestop, Bitcoin, they could go up 10x from here and it wouldn't even stop people buying them since they're not restrained by anything other than supply and demand.
Demand isn't going away any time soon.

We're only seeing the very beginning of the bubble, in my opinion. And we're sure to see an amazing crash when/if stocks crash back to their fundamentals. The longer it takes, the bigger the crash, but the more gains to be had on the way up.