in the house of Jacob: In the Old Testament, "Jacob" and "Israel" are often used interchangeably. They can refer to the patriarch or the nation.
To be foolish means to act rashly and immorally, ignoring consequences.
senseless: This literally means no heart. When "heart" is negative, it means a person or group does not want to do moral acts and rejects intelligent behavior that pleases God.
The people's ears and eyes worked (see study note on Jeremiah 6:10), but they stubbornly ignored the true meaning of what they heard and saw (Isaiah 6:9; Ezekiel 12:2; Mark 8:18).