There are quite a few centralized coins out there
For example, Ripple or Ethereum (and even Litecoin, to a certain degree, via Charlie Lee intervention), and the "controllers" have been exerting their power on a pretty regular basis. The famous Ethereum rollback is just one glaring example of that. But as I said it already, people won't care as long as the price will be rising. If it won't be rising, they won't care either whether this power is in fact NOT exerted at all. As no less famous saying goes, profits always trump prophets
to an extent that centralisation is actually appealing to the people who are into those coins. they've made no secret of it and enough people have accepted it.
bitcoin's a different deal. it's a boiling frog scenario. it really did start off decentralised and that's slowly falling away. if it gave up on it completely what virtues does it have left?