Which is why we must be vigilant against any attempts to takeover Bitcoin. They've already tried once with SegWit2x aka GarzikCoin, and if they have succeeded, we'd be on a road to what you're describing - a completely centralized system with exchanges serving as servers, together with miners. I think the big players of Bitcoin ecosystem, together with governments can try to repeat the attack, because the payoff can be huge while the costs don't seem to big - just spam the network and hire some shills.
I wonder how it would play out if this was looking like a real possibility. The most vigilant people are becoming increasingly obscure.
The big willies swinging around must surely know the core value proposition evaporates the moment it's irrevocably hijacked. The mindless traders won't care as long as the dollars keep pouring in. We can clearly see that no one cares about this in altland. 51% attacks don't seem to phase anyone.
Is there enough collective greed and blindness to barely acknowledge it when it happens? Will it become yet another zombie market propped up by the unwillingness to admit what it is at heart? Is BTC separate enough for it not to be allowed to happen?
Let's hope we never find out.