> The further the S&P 500 strays from reflecting the actual market, the more useless it becomes.

Here I once again agree with you in part, and disagree in part.

The S&P 500 should reflect the actual market. That is, the actual market of publicly-traded companies with legal requirements for transparent accounting and reasonable expectations of future positive cash flows.

As you wrote yourself (https://news.ycombinator.com/item?id=48408363), "These [mega-cap IPO] companies will likely never meet S&P profitability inclusion criteria for the next 5 years."

At this point in time, I don't think it's reasonable to expect future positive cash flows from SpaceX or Anthropic. There are indeed some reasons to suspect that there won't be future positive cash flows from them.