- no miner can say which transactions he wants to approve
But mining pool (admin) does.
I guess you are saying about transaction censorship. Yes, an admin of some mining pool can pursue his own policy and restrict some transactions even if they offer high fees, but the admin of other mining pool won't comply with such policy and will approve any transaction he wants. Therefore the transaction censorship is surmountable in the long run.
No, I've been talking about 'de-/centralization' in general.
In the long run one may find a way to launer money or fund terrorism even with current centralized banks so this argument is negligible.
Not only censorship, there are or might be some sort of transactions/messages valide from the protocol point of view but not implemented in pool SW (or switched off by default) which makes it no way to perform even if both - sender and receiver - are agree on it.
As I said, the true decentralization is an agreement among all participants concerned and none else.