"The People of the Book ask you to bring down for them a Book from the sky. Certainly they asked Moses for [something] greater than that, for they said, ‘Show us Allah visibly,’ whereat a thunderbolt seized them for their wrongdoing. Then they took up the Calf [for worship], after all the manifest proofs that had come to them. Yet We excused that, and We gave Moses a manifest authority." Quran 4:153
Those who insist on Shirk and die with Shirk will not be forgiven, but those who repented and left Shirk will be forgiven.
Millions of people who committed Shirk,then became Muslims, were forgiven.
The Hadeeth says: Believing in Islam cuts off whatever was before it الاسلام يجُبّ٫ ما قبله