Maybe you know this already, but this reads like exactly the kind of reasoning that people looking back at irrational market euphorias point to as a sign things were about to go awry.
It's not S&P's fault this is happening.
There are indices for every little thematic and niche corner or strategy or idea, there are broad-as-possible indices, and there are indices with requirements like listed age and profitability.
This discussion is about if S&P500 actually achieves this benchmark, when it has (antiquated) rules that exclude large-cap US companies of the likes of SpaceX, Anthropic, and OpenAI.