I'll offer an optimistic take on both of your concerns: 

1. I believe that most nostr clients will implement some form of outbox support. All Primal clients certainly will. We are literally a few days from releasing a major update. Once users’ notes are spread out over hundreds (eventually thousands) of relays, client devs will be incentivized to upgrade their clients accordingly. It will take a bit of time, but that’s okay. 

2. Nostr being seeded with bitcoiners is a feature, not a bug. To bootstrap a truly decentralized network, we need the initial group of users who understand decentralization and are willing to fight for it. There is no other way imho. The short term price we are paying is that the content is bitcoin-centric, but that’s fine. That will get sorted out over time as the network grows. 

IMO, we need to lower our time preference and be more patient. Everything is moving in the right direction. 

We don’t need a successor protocol. Nostr is the one we’ve been looking for.