I am a strong believer in low-cost index funds. These days there are exchange-traded funds which act just like stocks, but are really low cost index funds.
A lot of people do pretty well just buying and holding SPY, which is a S&P 500 fund.
If you are more venturesome, QQQ is the NASDAQ 100 fund, which is a lot more volatile than the S&P 500. More gains in good years, more losses in bad, but over the past decade, certainly more gains.
Put half your money in each one and pretend you are Rip van Winkle.
Send the "professionals'" kids to community college and retire like a prince.
Good advice.
All I know is after a quarter of a century, I would have done almost as well just stuffing it in a pillowcase. Which is still an option, I suppose!