From a humanist perspective, for our own short-term good, it might be morally wrong to suspend immigration.
From a more universal perspective, continuing to push for more immigration, more demographic replacement and more "economic growth", might be our most morally corrupt and downright horrendous act, so far. An act of utter greed and gluttony. We've chosen to further "human diversity" at the cost of biodiversity. And all of that may eventually play towards our own end.
We've lost control of our systems and are no longer in charge. We just hope someone is. Someone with a bigger brain than us, maybe an AI that can continue to keep feeding the monster. Or maybe just put it down, for the sake of everything else.