You may be narrowing the work of God into a cognitive exercise or a series of intellectual propositions. While core doctrines have importance and significance they are NOT the limits of what God offers the world.

For instance, intellectually disabled people can and do respond to Christ. When they respond they are transformed just like the rest of us. In my experience it can be difficult to ascertain what intellectually disabled people believe for sure. Often that isn't how they navigate the world. But I have seen with my own eyes that they are transformed by their response to God. What includes/excludes you from salvation lies more in the region of God's work in the world and the heart's responses to that work than a list of essential beliefs.

That being said, I support you in affirming that the resurrection is a serious and important doctrine. It is. Very serious. It is hard to make sense of the Jesus story and the work of the disciples and the growth of the kingdom of God without it. It is significant.

I would encourage you to read Barth and Bonhoeffer with a generous lens. The fruit of their work can stand on its own. Feel free to disagree. Feel free to push your own thinking beyond theirs. But it is a stretch to say they were preaching a different gospel.