Judah's mourning looks real, but it seems they're more cut up about the drought, and subsequent lack of water, rain, vegetation, than their sin.
Jeremiah's prayers are real: he realises that Judah's iniquity testifies against them (14.7, 20), yet he calls on the LORD to act, 'for your name's sake' (14.7). He calls on the 'hope of Israel, it's saviour in time of trouble' (14.8) and his prayer is bold: why should the LORD be like a warrior who cannot save, like a stranger in the land. But the time for turning away has passed, and Jeremiah is told not to pray for the people (14.11), their fasts, cries, and offerings are to no avail.
And the false prophets who denied God's judgement and told of assured peace in the land? They will face the judgement that they so deceitfully denied (14.14-15).
The Lord is not slow to fulfil his promise as some count slowness, but is patient towards you, not wishing that any should perish, but that all should reach repentance. But the day of the Lord will come like a thief, and then the heavens will pass away with a roar, and the heavenly bodies will be burned up and dissolved, and the earth and the works that are done on it will be exposed.Time was up for Judah. Time will soon be up for the world.
2 Peter 3.9-10
All the time in the world?