Obviously if you have temporal language, at some point, an event which a text foretells in the future is in the present, and at a point after that, it's in the past. That doesn't mean that the scripture is "incorrect," it means that it was written at a particular point in time which has passed.
Deuteronomy 18:15 says that God "will raise up" -- future tense -- for Israel a prophet like unto Moses. Is that event still in the future, or was it realized in time when Christ came, and therefore now in our past? And if God has now sent the prophet like unto Moses, does that mean that the Scripture was correct, and now is not?
Of course not.
Again senseless. Paul was writing to fellow Christians. Paul and the people he was writing to were all under the new covenant. If Paul believed that the holy days WERE shadows, he had no reason not to say so. After all (according to you) the old covenant was over for Paul. Presumably (according to you), they weren't participating in any of the priestly services. They WERE shadows to him. But still, he said ARE. Why?