That means the perennial prophets of doom.
Here is an example: Trump calls climate activists ‘perennial prophets of doom’ during Davos economic forum.
“This is not a time for pessimism. This is a time for optimism. Fear and doubt is not a good thought process because this is a time for tremendous hope and joy and optimism and action.” I would translate that into German but German just doesn’t have that kind of vocabulary.
„Wir müssen die ewigen Propheten des Untergangs und ihre Vorhersagen der Apokalypse zurückweisen.”