Yes, but the point is, if startups were very meritocratic, then other people who didn't have powerful parents would build bigger businesses and outshine them, f

Yes, but the point is, if startups were very meritocratic, then other people who didn't have powerful parents would build bigger businesses and outshine them, for the simple reason that people without powerful parents outnumber those with powerful parents by a margin of something like 30:1. The only alternative explanation is that people with better parents are more talented, and there is indeed a correlation there, but it's fairly weak, and there's no reason to believe that technical talent is more heritable than political or singing or acting talent.