Isaiah sees the Lord "high and lifted up" in his vision (6:1). Representing Judah, Isaiah is below; Yahweh is seated on the throne and Isaiah is not. Judah, who was so sure of her security based on riches, military might, coalitions with nations, and her appropriate rituals, finds that she is in no place at all to manipulate God.
Notice, Isaiah does not break into deep fits of awe and worship and "this is so incredible to be here." Isaiah's response rather is immediately, "Oh no."
The time of reckoning had come.