It's generally a mistake to trust the financial advice of any hedge fund manager, and they usually provide advice that makes the S&P seem like a bad bet.
Time will tell whether said speculation will turn out to be right. However, if more people believed such speculation, it might make it more likely to be right in the future. Therefore, there's a selfish reason for said person to promulgate such speculation.
Looking at the S&P anywhere in the past 100 years makes it look like a pretty solid bet (not even a bet really).
No one ever became wealthy from buy and hold index funds. The returns are relatively low because most people are lazy and it's the easy thing to do. That's why I split my time between active investing (https://grizzlybulls.com) and working on my private business ventures.
Nobody ever became poor from it either (unless they panic). At least your money keeps pace with inflation to some extend. It certainly beats the money sitting in your bank account doing nothing (the alternative for most people).
e.g. it took 30 years to recover to 1929 levels, then also 30 years to reach the 1960’s peak, in 2010 it fell to mid 90’s levels (all inflation adjusted).
So yes, you’re right but it depends on how long you can wait. Over 50-60 years you should be fine. 20-30 who knows, if you’ve entered just before a peak it might not recover within your lifetime.