Islam does teach that Jesus, son of Mary, will return near the end of time, but not as a rival to Prophet Muhammad (PBUH), not as God, and not with a new religion. His return is a sign that confirms Islam's account of him and the finality of the Prophet (PBUH).
Why the question has force
The objection is understandable. If Prophet Muhammad (PBUH) is the final and greatest messenger, why is Jesus the one who descends, defeats the Dajjal, and rules with justice? Critics say this looks like Islam quietly needs the kingship of Jesus while denying the Christian claim that he is divine Lord.
That is the strongest form of the argument: Jesus seems to receive a unique end-times role that, at first glance, appears too large for "only" a prophet.
What Islam actually says about Jesus
Islam does not "demote" Jesus in the sense of belittling him. The Quran calls him the Messiah, a word from Allah, born miraculously of Mary, supported by miracles, and among the great messengers. What Islam denies is not his honor, but his divinity and sonship.
"They did not kill him, nor did they crucify him, but it was made to appear so to them... Rather, Allah raised him to Himself."
Quran 4:157-158
"There is none from the People of the Scripture but that he will surely believe in him before his death, and on the Day of Resurrection he will be against them a witness."
Quran 4:159
Many classical exegetes understood this as connected to Jesus' return before the end of time. So his descent is not an awkward later addition to Islamic belief; it flows from the Quranic claim that he was raised and that the truth about him will be made plain.
He returns as a follower, not a new lawgiver
The hadith are explicit that Jesus returns as a just ruler and judge, but within the final religion brought by Prophet Muhammad (PBUH). He does not bring a new scripture, cancel the Quran, or resume a separate dispensation.
"By Him in Whose hand is my soul, the son of Mary will soon descend among you as a just judge. He will break the cross, kill the swine, and abolish the jizya."
Sahih al-Bukhari and Sahih Muslim
"Break the cross" means he will publicly refute the false belief that he was crucified and worshipped. "Abolish the jizya" is understood by scholars in the context of that final age: the truth will be manifest, and he will rule by justice under Islam.
This does not contradict the finality of Prophet Muhammad (PBUH):
"Muhammad is not the father of any one of your men, but he is the Messenger of Allah and the seal of the prophets."
Quran 33:40
A previous prophet returning is not the same as a new prophet being sent. Jesus' return actually confirms the seal of prophethood, because he comes under the law of the final messenger.
What this proves and what it does not
Jesus' unique return proves that Islam gives him a special end-times role. It does not prove that Islam secretly affirms his divinity, nor that prophetic honor must mean divine kingship. In the Quran, Allah alone is the final Judge of mankind. Jesus judges on earth as a righteous human ruler by Allah's permission.
Different prophets have different distinctions: Abraham is the intimate friend of Allah, Moses spoke to Allah, Jesus was raised and will return, and Prophet Muhammad (PBUH) is the final messenger to mankind. Difference in role is not incoherence.
So the Islamic answer is plain: Jesus returns because the greatest confusion in religious history gathered around him, and Allah will make the truth about him unmistakable before the end. His descent does not weaken the message of Prophet Muhammad (PBUH); it vindicates it.