The "power of compounding" still occurs. For those who invest regularly and use a dollar cost-averaging strategy, the recent slumps in the market represent a buying opportunity--the ability to but stocks, mutual funds, and ETFs at a discount. They're getting more shares for their money now, and the accumulation of shares is where the real "compounding" occurs.
The markets don't always go up.
What you gave is the argument that everything is fine, for those in the upper-echelons who choose a good broker. For the middle and lower middle classes, it's what they can do on their own, and the stock market is not where they should be playing with their often meager life savings.