In the modern church in the West, there has been a large shift away from believing core, essential, orthodox truths and a turn to adopt the methods of the culture to try and reach the culture for Christ. In the process, Scripture and its divine authority gets put on the shelf, collecting dust. While this may seem wise on the face to try to reach the culture with modern cultural ideologies and techniques, what ends up happening is that the church becomes so indistinguishable from the world that it no longer possesses the doctrinal distinctiveness it needs to spread the Gospel with clarity that people may be saved. This is very dangerous, 1) because you begin coddling people into the church that may never be converted (because of the indistinguishable, worldly message being preached), all the while assuming they are converted because they take the name “Christian,” and 2) the light of the Gospel gets snuffed out because of worldly doctrine being taught, and 3) ultimately God’s glory is suppressed as a result (Romans 1:18-19).
The Cambridge Declaration is simply a modern reassertion of core, essential doctrines that must be affirmed by every believer. In fact, they are really not speaking of anything new, but reasserting the very doctrines the Reformers themselves recovered from the dead Roman Catholic church. This statement basically goes through the Five Solas of the Reformation, explains them, and then applies them to the modern crisis the evangelical church in the West is facing. And the crisis is that we are on the verge of becoming totally irrelevant to our culture (just as it has already happened in Europe to a great degree, what is it now, 2% confessing Christianity?)