Programmatically delete blocks

delete_blocks.php

/**
 * Delete unwanted blocks programmatically.
 *
 * @param array $blocks
 *  Array of block UUIDs for deletion.
 */
function _delete_blocks(array $blocks) {
  foreach($blocks as $uuid) {
    $block_content = \Drupal::service('entity.repository')->loadEntityByUuid('block_content', $uuid);
    if (!is_null($block_content)) {
      $block_content->delete();
    }
  }
}

/**
 * Delete unwanted blocks.
 */
function DEMO_helper_update_N() {
  $blocks_to_delete = [
    '071d37ca-0157-4d50-a4a6-66ec7facc153',
    '16361ba0-a298-471b-a7cc-32f61873fb0d',
    '5681f213-6d9b-4bf5-9313-789c3c21ba5a',
    'fb258b89-3f79-433a-95a7-9c437db81035',
  ];
  _delete_blocks($blocks_to_delete);
}