YC's founders also skew heavily towards a certain type of person and business. The returns of VC in biotech for example are much lower than the returns in B2C and B2B software. It's just a harder, more capital intensive, and more uncertain industry. Over optimizing for the YC archetype means you get less of the people who succeed in other areas.
Also, although PG disdains finance and management, many large problems are better addressed through people with skills in these areas IMO, since often the returns are not sufficient to attract VC interest but the financial and human resources that need to be coordinated to address them are substantially beyond the ability of a small, undercapitalized group.