Also remember that this isn't the first time this idea of 'lets rollback a blockchain due to a hack/attack' has been floated or even tried. The first major blockchain rollback almost completely destroyed the cryptocurrency [1]. Since then, some major hacks have happened and the community/developers rejected the idea of a rollback [2][3]. That was a hard lesson, and hopefully the current developers will learn from the short history.
Also to your point, yes, Ethereum is not as decentralized as some would like to claim, either from a stakeholder perspective, or from a mining perspective, or even from a 'who holds the power' perspective. I suspect that's what makes it so efficient though, in terms of changing protocol, or making decisions on behalf of stakeholders.
One could argue that at this point in its history it stands to benefit more from that efficiency than it would from more robust decentralization.
When adoption is low it stands to reason centralization would be high, and so it enables them to move faster to increase adoption, and hence lower centralization as other players and stakeholders enter the game.
However it does also stand the risk of allowing the current influential parties (the developers or miners) to influence the system in their favor. So far though, I don't think this has been the case, but we'll see how this situation plays out.
There is no doubt that centralization is more efficient than decentralization. The problem comes when developers or other stakeholders don't understand or underplay this feature.
Also, centralization/decentralization is a a scale, not discrete boolean values.
It will definitely be interesting to see how this plays out. Good luck to everyone involved.
Also to your point, yes, Ethereum is not as decentralized as some would like to claim, either from a stakeholder perspective, or from a mining perspective, or even from a 'who holds the power' perspective. I suspect that's what makes it so efficient though, in terms of changing protocol, or making decisions on behalf of stakeholders.
[1] http://247cryptonews.com/vericoin-lack-integrity-bailout-min...
[2] https://www.cryptocoinsnews.com/official-nxt-decision-blockc...
[3] http://www.newsbtc.com/2014/12/17/opal-recovers-1-7-million-...