However, I do think market cap is a reasonable proxy as factors like growth (which can strongly impact market cap) have interesting implications for where an entrepreneur should or should not build a business.
Market cap is a proxy that has too many outside factors and should be eschewed in favor of more concrete and reliable numbers since they are readily available.
I agree with you that a more complex analysis could be done and it would be more rigorous and it may reveal additional insights.
However, I am guessing the primary takeaways I listed would not change much with the additional rigor.
Your comments also raise an interesting question - i.e. what are the right measures by an entrepreneur for the value their company is creating? There are obvious points of human impact (user base, engagement etc.), but if you are an entrepreneur, what financial metric should you care about? For example, Jeff Bezos often point to free cash flow as the big metric Amazon tracks...