To get into heaven, yes. God could have set it up differently, but he didn’t. We don’t need Jesus (that is, we don’t need for God to have become incarnate and die and rise) to do many things that we do. We can breathe and eat and such without the incarnation having happened. We aren’t getting to heaven without it, though.
Each man/woman in heaven will be incorporated into Christ. The angels were in heaven without the need of the incarnation, though, so they are not in the same situation as us, that is part of why I asked you, to see if it was the angels you were interested in.
In the end, all things are given to Christ. All things are brought together in Christ. God set it up that way. Maybe it would help to remember that “through him all things came to be, and without him, nothing that came into being came to be” from the gospel of John. “In him was life, and that life was the light of men.” He’s the one with the life as per God’s plan.
Oh, also it might help to remember that prior to Jesus, all the Old Testament righteous people were not in heaven. They were waiting. After the crucifixion, Jesus opened the gates of heaven.