Yes, a diversified investment portfolio could perform like that in the past, when the gov't wasn't minimizing interest rates. Nowadays only with much greater risk of loss of principal.
The S&P 500 is up about 7% annually over the last 5 years, with inflation never exceeding 3% over that period. That leaves a calm 4% real return on one of the less risky investment options.
About the same... Over 10 years the S&P is up 83.6% excluding dividends. Going back to July so month to month comparisons are valid it looks like the annualized return is 6% excluding dividends and 8% including them.
Agreed. With a lot of risk for that reward. The risk shows in the volatility (ups & downs) over that time, and that the gov't had to borrow several $trillion to prevent a negative return over that time.