This song has an important melodic parallel with the entrance antiphon for Christmas Day, Puer Natus Est. Both songs announce the arrival of a king and in similar ways. Both are Mode 7 chants (modes matter!) and they follow a similar formula. This is not an accident. Keep in mind that it was only after Christ’s death and resurrection that it become clear precisely what kind of King he would be.
If we leave out both songs, some important liturgical/theological information is lost.