...the S&P500 has now become some sort of a joke to be...

...the S&P500 has now become some sort of a joke to be representative of market performance.

...it is therefore conceivable that we may have many stock crashes not appropriately captured and reflected in the S&P500, as long as the big fab 4 mega tech stocks continue to outperform with their moat.
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The chart shows the change in the S&P 500's market capitalization, which is a good proxy for the returns calculated by S&P.
This "simple" market capitalization change is up 9.16% YTD. 3.58% of this is gain NVDA. That's 39% of the S&P 500's gain YTD!
AMZA, MSFT, and META account for another 1.41% of the S&P 500's gain YTD, or 15%.

54% of the S&P 500's gain YTD is just four stocks!  These four stocks account for just 19% of the total market capitalization for the S&P 500.