It does not say the time of israel was over. Not even hinted at.
Every prophet in the OT, even to John the Baptist, offered Israel opportunity for repentance.
Stephen did not.
KJV Acts 7
51 Ye stiffnecked and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye.
52 Which of the prophets have not your fathers persecuted? and they have slain them which shewed before of the coming of the Just One; of whom ye have been now the betrayers and murderers:
53 Who have received the law by the disposition of angels, and have not kept it.
This was an indictment like no other. No mercy. No forgiveness. No call to repentance. Merely an accurate historical and judicial summary of the charges being laid before them. They trusted in their temple, their services, their sacrifices.
KJV Acts 7
48 Howbeit the most High dwelleth not in temples made with hands; as saith the prophet,
49 Heaven is my throne, and earth is my footstool: what house will ye build me? saith the Lord: or what is the place of my rest?
KJV Matthew 23
38 Behold, your house is left unto you desolate.
Note well, not my Father's house... Not my house...
Your house is left into you desolate.
As a nation chosen of God for the purpose of bringing the gospel to the world, their employment was over. Their 70weeks of probation was over. Israel had not onl y killed the prophets who told of the coming Messiah. They killed the Messiah when he came.
Read Mark 12:1-12. Pay particular attention to verse 9.