If you want sobering reading in Scripture, read all the occurrences of the words "how long" in the Bible.
"How long" are words of lament. They appear as in Habakkuk 1:2, "How long, LORD, must I cry for help? But you do not listen! I call out to you, 'Violence!' But you do not intervene!" And in Psalm 13:1-2, "How long, LORD, will you continue to ignore me? How long will you pay no attention to me? How long must I worry, and suffer in broad daylight? How long will my enemy gloat over me?" When I meditate on how far this world is from the kingdom of God both at the macro-level and at the level of individual words and actions by individual people, I grieve and ask God, "How long?" myself.
But "how long" appears more often not addressed to a seemingly aloof God but as God's lament over stubbornly sinful people. "How long will this people despise me, and how long will they not believe in me, in spite of the signs I have done among them?" (Num. 14:11). "How long will [false prophets] go on plotting to make people forget who I am through the dreams they tell one another? That is just as bad as what their ancestors did when they forgot who I am by worshiping the god Baal" (Jer. 23:27). Verses like this make me shut my mouth. How often has God mourned, "How long?" while looking upon my words, thoughts, and deeds that don't measure up to the treasure of his Holy Spirit within this crumbling vessel?
God alone knows how long. My confidence today is in his promise, "And the glory of the LORD shall be revealed, and all flesh shall see it together: for the mouth of the LORD hath spoken it" (Isa. 40:5). This will happen, because God says so. Oh, God, may it be, and may it be soon.