Automation to unassign people periodically but only if status is not "done"

I am looking to automatically unassign all people from subtasks when the status is not “done” once a day.

The idea is to be more agile and respond to ressource-shortages better.
More precisely every evening the columns should be cleared so we can assign whoever is available the next morning to the most pressing projects.
I don’t want to clear subtasks which are already done for various reasons, however.

So far I am always confronted with the issue that “every time period” automations are not compatible with additional conditions.

Thanks for any info how to achieve this.