if their new doctrines are inspired, why doesn't the Lord direct us to add them all to the Bible?
No one should be adding new doctrines to the faith. The faith was 'once delivered to the saints.' That is one of the problems with the ideas you are promoting. You don't even have a real proof text for some of them. For example, you don't have a proof text at all for the idea that miracles ceased. You haven't shown a single verse. i asked for one, and you showed a passage that doesn't mention miracles ceasing at all. I wonder if you actually see the words there in your mind, words that aren't on the page.
Adding doctrines to the Bible and getting prophecies are not the same thing, btw. I could give you a long list of prophecies and revelations that are alluded to in the Bible, but the words aren't written there. Whatever the seven thunders said was a revelation, but it was not written in the Bible. John was told to seal them up. Samuel was established as a prophet in Israel between that one prophecy we read that he gave about Eli and the time he was an old man, but we don't know what he prophesied. He told Saul that prophets would meet him. They prophesied, but we don't know what they said. The text of Saul's prophecies aren't recorded in scripture, either.
Micaiah prophesied the death of Ahab. Before he did, Ahab told the king of Judah the reason he hadn't brought him out was because, "He never prophesies anything good about me." We don't have any of Micaiah's previous prophecies in scripture. We don't have the prophecies of the sons of the prophets, or the prophecies of established prophets who show up for brief episodes.
The argument that, "if you get a prophecy, you have to add it to the Bible" doesn't hold water because the Bible doesn't contain all prophecies. It doesn't contain all revelation that God has given. All of creation doesn't fit on our shelf, and God has revealed Himself through creation, too, so that, like Romans 1 teaches, men are without excuse.