Al-Asha`irah are not considered of Ahl-ul-Sunnah because they do not affirm Allaah’s Attributes:
17- Al-Saaboonee mentioned in his sixth article, which opens with his saying: “This is a plain statement for mankind. The Ta’weel (allegorical interpretation) of some Aayaahs and Hadeeths on Attributes does not rule the Muslim out of Ahl-ul-Sunnah wal-Jamaa`ah (adherents to the Sunnah and the Muslim mainstream), since some of them are wrong while some others are right. Moreover, there are explicit Aayaahs on Ta’weel that were allegorically interpreted by the Sahaabah (Companions of the Prophet), the Taabi`oon (Followers, the generation after the Companions of the Prophet), and the Salafee scholars. No one could dare accuse them of aberration or rule them out of Ahl-ul-Sunnah wal-Jama`ah.” Then he gave examples of this, including Allaah’s saying: They have forgotten Allaah, so He has forgotten them. The examples also include Aayaahs on Allaah mocking at the mockers, scoffing at the scoffers, and planning against the plotters, and also the authentic Hadeeth about Allaah’s saying: I was sick but you did not visit Me and I was hungry but you did not feed Me. He went on to say: “Thus, the case is not like what some people think, namely, that the Madh-hab of the Salaf (righteous predecessors) does not involve Ta’weel at all. Rather, the Madh-hab of the Salaf requires allegorical interpretation of what should inevitably be allegorically interpreted.”
Answer: This claim requires detail. It combines truth and falsehood, for his claim that applying Ta’weel to some of Allaah’s Attributes does not remove a Muslim from Ahl-ul-Sunnah is generally true, since the person who applies Ta’weel to some of Allah’s Attributes, such as Al-Asha`irah, is not consequently removed from the Muslims or Ahl-ul-Sunnah, as regards matters other than the Attributes. Yet, he is not included in Ahl-ul-Sunnah when it comes to affirmation of the Attributes and disaffirmation of Ta’weel. Al-Asha`irah and their like are not included in Ahl-ul-Sunnah as regards the affirmation of the Attributes, since they disagree with them in this matter and assume different approach. This, however, requires repudiating them, exposing their mistake as regards Ta’weel, and explaining that it contradicts the approach of Ahl-ul-Sunnah wal-Jamaa`ah, as is already stated in the first of the present notes. There is no problem in saying that Al-Asha`irah are not among Ahl-ul-Sunnah as regards Divine Names and Attributes, even though they are among them as regards other matters. In this way, anyone reviewing their Madh-hab would recognize that they make a mistake when they applied Ta’weel to some Attributes and thus disagreed with the Sahabah and those who righteously followed them in this matter. This, in turn, would imply confirmation of truth and setting Ahl-ul-Sunnah and Al-Asha`irah in the positions where they really are… read more here.