Index: src/wp-includes/class-wp-list-util.php
===================================================================
--- src/wp-includes/class-wp-list-util.php	(revision 51609)
+++ src/wp-includes/class-wp-list-util.php	(working copy)
@@ -102,7 +102,8 @@
 		$operator = strtoupper( $operator );
 
 		if ( ! in_array( $operator, array( 'AND', 'OR', 'NOT' ), true ) ) {
-			return array();
+			$this->output = array();
+			return $this->output;
 		}
 
 		$count    = count( $args );
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 51625)
+++ src/wp-includes/functions.php	(working copy)
@@ -4903,6 +4903,7 @@
  *
  * @since 3.1.0
  * @since 4.7.0 Uses `WP_List_Util` class.
+ * @since 5.9.0 Converted into a wrapper for wp_filter_object_list().
  *
  * @param array  $list     An array of objects to filter.
  * @param array  $args     Optional. An array of key => value arguments to match
@@ -4914,13 +4915,7 @@
  * @return array Array of found values.
  */
 function wp_list_filter( $list, $args = array(), $operator = 'AND' ) {
-	if ( ! is_array( $list ) ) {
-		return array();
-	}
-
-	$util = new WP_List_Util( $list );
-
-	return $util->filter( $args, $operator );
+	return wp_filter_object_list( $list, $args, $operator );
 }
 
 /**