Really appreciate your analysis. I haven't been on Hive for too long, but I dug pretty deep, and have made similar observations:

• I honestly don't think that quadratic voting would solve anything. Big accounts would split their holdings across multiple smaller accounts and continue to do the same. Also, from the perspective of a newly onboarded person, I wouldn't consider this an actual problem (it's the same everywhere)
• Revenue generation or the lack thereof is a real issue. Ads won't be the solution as they'd be application-oriented and can't power the entire ecosystem. So there would have to be other use cases, but that's inherently difficult to organize from a protocol perspective. On a different note, having applications that generate significant revenue outside of rewards would help a big deal if they then purchase large amounts of HIVE
• The most important aspect to me is actually a clear positioning of the ecosystem and respective marketing/business development. In a world where there's hundreds of relevant public blockchains (with new ones launching every month), you need to actively develop the ecosystem and attract / incentivize / help builders launch their products on/with Hive