Utterly means ^completely, totally, or to an absolute/extreme degree^.
Reject means ^to refuse to accept^.

Why has God totally rejected the Jews? Because they rejected Jesus, YHVH in the flesh.

This is clearly stating that YHVH has stopped relating to Jews as descendants of Abraham and now sees them as individual humans.

As individual humans they can be saved only by acknowledging that Christ Jesus is YHVH and receiving Him as their personal Lord and Saviour.

The OldCovenant is done. The NewCovenant is in effect.