Absolutely, plus since index funds are cap weighted, ordinary retirement fund investing folks are very much vulnerable to it.

If I pull up VTSAX (vanguard total stock market index fund) what I find is...

Sectors: Technology is 38% of the fund and I see 11 sectors listed.

Top 10equity holdings, in order from the top:

NVDA MSFT AAPL AMZN META AVGO (Broadcom) GOOGL TSLA GOOG BRK.B (Almost like its own index fund)

This is fine!!