Below are the 3-year, 5-year, and 10-year performance of RSP vs SPY. As you can see, a regular cap-weighted ETF or index fund has beaten an equal-weight ETF during each of these periods. The stock market has rejected the thesis of value investors who claimed, all these years, that the S&P 500 was "overvalued" relative to RSP due to a concentration of 5 megacap tech stocks constituting almost 20% of the index. Of course, this can change in future. But 10 years is a long time for a thesis to be wrong.

  
SPY vs RSP annualized returns
Period   SPY     RSP 
3-yr     8.6%    7.0%
5-yr    14.8%   12.3%
10-yr   11.5%    9.5%     

This is good news for investors with 401K plans, since most of these plans have a Vanguard index fund as an option, but not RSP.

Note that within the past 10 years, we've had 2 severe bear markets and a near bear market - the Covid bear market of 2020, the recent 2022 bear market, and the near bear market of 2018. The market has prevailed despite all these bear markets, Ukraine-Russia war, Israel-Hamas war, etc.

Note, also that Warren Buffett, who is not particularly known as an irrationally exuberant growth investor, maintains a 50% allocation of Apple (AAPL) relative to his entire equity holdings in Berkshire Hathaway.

As of today, December 21, 2023, Berkshire Hathaway owns approximately 915 million shares of Apple. Apple's current share price is around $178.45. Therefore, the market value of the AAPL shares within Berkshire Hathaway is roughly $163 billion, which is about half the total equity holdings there. Buffett certainly does not equal-weight his holdings.