... aren't scriptures SO VAGUE that prophecy could be interpreted as virtually anything you want?
In some cases, perhaps, but also in many cases, no. Prophecies tend to be specific and those who are familiar with the New Testament couldn’t miss the numerous prophecies pointing to Jesus in the Old Testament. Isaiah 53 is so specific that it sounds as though it was written in the First Century A.D.; however, there are many more prophecies. Look at the creation of Israel, which was scattered among the nations. The prophet Amos wrote: “And I will bring again the captivity of my people of Israel, and they shall build the waste cities, and inhabit them; and they shall plant vineyards, and drink the wine thereof; they shall also make gardens, and eat the fruit of them. And I will plant them upon their land, and they shall no more be pulled up out of their land which I have given them, saith the Lord thy God.” (Amos 9:14-15)
This prophecy was fulfilled literally when the Romans scattered the Jews among the nations of the earth and then gathered them back to their own lands. Then they will revitalize the land, as they’ve done, and Amos really goes out on a limb when he writes, “and they shall no more be pulled up out of their land which I have given them.” From there, jump to Zechariah 12-14, where the prophet predicts that after Israel is gathered, the Lord will go to its aid when it’s attacked: “Behold, I will make Jerusalem a cup of trembling unto all the people round about, when they shall be in the siege both against Judah and against Jerusalem. And in that day will I make Jerusalem a burdensome stone for all people: all that burden themselves with it shall be cut in pieces, though all the people of the earth be gathered together against it.” Israel has won some amazing confrontations when attacked by its neighbors (1948 and 1968 are notable examples). Armageddon will be the last battle of the region and the Lord will appear personally and destroy Israel’s enemies.
Isaiah also prophesied that Judah would be dispersed among the nations of the earth, then gathered back to the lands of its inheritance. He writes: “And it shall come to pass in that day, that the Lord shall set his hand again the second time to recover the remnant of his people, which shall be left, from Assyria, and from Egypt, and from Pathros, and from Cush, and from Elam, and from Shinar, and from Hamath, and from the islands of the sea. And he shall set up an ensign for the nations, and shall assemble the outcasts of Israel, and gather together the dispersed of Judah from the four corners of the earth.” (Isa. 11:11-12)
It’s difficult to overemphasize the accuracy of these prophecies. At the time they were given, they were preposterous. Even the Babylonian conquest and subsequent captivity, which was devastating to the Jews, didn’t begin to compare with the dispersion and restoration. In fact, Israel was not declared to be a nation again until 1948. But the Jehovah's Witnesses didn’t emerge until the late 1870s. The prophecy thus had not yet been fulfilled. So Charles T. Russell and later leaders had to spiritualize the prophecies so they didn’t point to the Jews and Jerusalem but, rather, to the church. And Armageddon, which was supposed to take place in Jerusalem against the Jews, instead was a worldwide conflagration between good and evil, or more specifically, between the Jehovah's Witnesses and the Devil. Even after the establishment of Israel as a state, they’ve continued to assert that Armageddon is a war between the church and the wicked; and they’ve made such a big deal out of it that even “new light” can’t change things.
The prophecies in scripture aren’t the strong point in JW theology. Members don’t know them and don’t study them. I’ve read a number of articles on Armageddon in the Watchtower and other publications, including the Bible Study book and The Truth That Leads to Eternal Life, and I’ve always come away astounded how little is known about the real Armageddon.
Based on the stunning accuracy of biblical prophecies already fulfilled, prophecies yet unfulfilled have an excellent chance of coming to pass. Jesus also foretold the fate of Jerusalem and the Jews, and when the Romans came down on the city, the Christians were all ensconced in Pella and other cities to the north where their leaders had led them. As Jesus had told them in His day, when the time came, “Stand ye in holy places.” Some might have thought that meant the temple, but “holy places” meant anywhere that was designated by revelation.