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?
Because, unlike you and your fellow messianics, and unlike modern Jews, Paul could actually go to the temple and witness firsthand, actual, live biblical rituals straight from the law of Moses, animal sacrifices included. They are shadows to him because they still existed in that day and folks could still be trapped in them from recognizing Messiah.
They are no shadows today simply because no one is able to keep a Mosaic feast according to strict biblical commands. There are ersatz feasts, shadows of a type, that some folks are enamored with.