Rashi: The Navi says, the ones to whom I speak are poor in Chachmah.

Radak: I reckoned, when I rebuked them and they did not accept, they are lowly and foolish. They do not have much Da'as and understanding. They tend vineyards and fields. Their only engagement is working the land. They disqualify engage in Musar, Torah and Chachmah. Therefore they did not accept rebuke!

Malbim: They are not Mezid, just they lack knowledge. To know that a punishment came for rebellion, they must know (a) that they sinned. They do not know Hashem's way, They do not know what is Mitzvah, and what is Aveirah! (b) They must know that the punishment is Hashgachah, and not chance. They do not know Mishpat Elokim, to realize that it is Hashgachah! They think that their poverty caused all the evil to them. Therefore, punishment and rebuke will not help.

Rashi, Targum Yonasan: It is foolish ¹ . It is from the root Evil.