The chance of another distributed platform with the properties desired seems small. Why should email be resistant to any change? Takes like this is why every company develops their platforms as silos rather than open standards. To avoid the inability to ever make a change once it becomes popular. Instead, at best, we end up with large monocultures around an open source project such as Linux or chromium. Maybe that's better and email like platforms are a mistake, but fundamentally I don't feel like that should be true.