There was a pretty strong bull market leading into 1973 which then began the worst bear market since the great depression, lasting until November of 1974.
Then the market bounced and a strong bull market ensued. Net inflation and price over a long period one could argue the market was flat or down, sure, but on a year-to-year basis to argue there was no money to be made or lost holding stocks during this period is just wrong.
If you were clever enough to get out of the market early in the 73-74 bear market and then get in relatively early after the November of 74 rebound, you'd have certainly had good returns. If you think that's just hindsight and nobody could've done that, read Marty Zweig's Winning on Wall Street where he has a section entirely devoted to that period and how he did avoid most of the drawdown.