That's the thing though. I think this attitude is incredibly pervasive in tech more broadly. No one hires juniors. They don't want to train and invest in inexperienced employees. Instead firms will hire seniors, milk them for every hour they are willing to dedicate.
Those that care give it their all and burn out after only a couple years. Especially when they see their extra efforts go unrewarded. The burnt husk of a human that comes out the other end will usually quit for greener pastures and the chance to start fresh where they are hopefully recognized. They are now someone else's problem.
Then you end up with the poor souls that have experienced this cycle 2-3 times, don't give a shit and just coast by giving the firm the minimum effort to avoid a bad performance review.
Unfortunately I think the current tech culture is very hostile to anyone who is young or cared.
They didn't say anything about implementation. Why couldn't you build tooling to keep it decentralized? Servers or even communities could choose to ban from their own communities based on a heuristic based on the moderation actions published by other communities. At the end of the day it is still individual communities making their own decisions.
I just wouldn't be so quick to shoot this down.