Firstly note that my answer says that "some" of the Mu'tazilah held that opinion. It is not the opinion of Mu'tazilah as a whole. As @Medi1Saif has noted in the comments, Zamakhshari in his tafsir has rebutted the arguments of those who held the contrary belief.
Their evidence (as mentioned in e.g. إكمال المعلم بفوائد مسلم and شرح النووي على مسلم) is that they have relied upon the Prophet Muhammad ﷺ being the last of the Prophets:
[Muhammad is the] last of the prophets
— Quran 33:40
لا نبي بعدي
There will be no prophet after me
Their argument being that if it is accepted that Jesus عليه السلام is sent back, then he would be the last prophet not Muhammad ﷺ.
The response to that is that the meaning of being the last prophet is that he is the last one to whom prophethood was granted. Jesus's prophethood and ministry came before Muhammad, and his second coming is not in the role of a prophet or to give new revelation, but rather as a caliph to implement the shariah of Muhammad ﷺ.