True, and today he is still making his power known. People are still being healed, miralces still happen. It is just that they are all dismissed are coincidences, or if they cannot be dismissed as coincidences, they are just denied ever happening. Except by the people who personally witnesses them.
I have a few problems with the concept of these being miracles, both morally and practically.
Let's cover practically: Yes, there is a huge list of people who were crippled, terminally ill, etc who have been "miraculously" healed. However all of them contain some element of doubt. I have not seen a single reference in any reliable documentation where someone has unquestionably been healed miraculously. There are no cases where a missing limb or eye has spontaneously reappeared, which would unquestionably be a miracle. It seems suspicious to me that only things which do not involve a blatantly visible change are healed miraculously.
Now for morally: Most religions state categorically that God is omniscent and omnipotent. If God is omnipotent, why does He only miraculously heal an absolutely tiny minority of those who need it. You could argue that every other person who is ill has committed some terrible evil, but given the number of ill newborn children (who incidentally seem to get far less than their fair share of miracles), I don't think this is the case. This strongly implies that either God has the power to heal all the sick, and chooses not to, which is morally unacceptable to me, or God is incapable of healing them. This is obviously not acceptable to any religion, as it would require a God who was not only not omnipotent, but far too weak to perform acts like creation and ultimate judgement.
The only option I can see that is remotely morally acceptable is that God is no longer capable of influencing this universe now for good or ill. Rules must be applied fairly, and if he is capable of helping all the sick he should do so, not just help a tiny minority. Strange as it may sound, I would be very sad to see a genuine miracle, as this would be unquestionable evidence to me that God is either not omnipotent, or is of poor moral fibre. In God's favor though, I have seen no definitive evidence of a genuine miracle, so maybe he is applying the rules fairly.