We can see this at work even today. God is maintaining His state of being hidden from the people of Israel—but the Father is revealed through Yeshua HaMashiach (Jesus the Messiah).
The message of the Day of the Lord, then, is that it’s coming is inevitable. Its harshness, though, is directly related to our disobedience to Yahweh: The greater the disobedience, the greater the destruction; the greater the righteousness, the greater the blessing.
Hopefully, if you know how to rightly divide your Bible, you can see why it is simply not possible to take the Second Coming prophecies of Joel 2 and 3 and try to place them on the Church.