Disallow all and allow only specific blocks

function king_disallow_block_types( $disallowed_block_types, $block_editor_context ) {

    $allowed_blocks = array(
        'core/heading',
        'core/paragraph',
        'kadence/accordion'
    );


    if ( ! is_array( $disallowed_block_types ) || empty( $disallowed_block_types ) ) {
        $registered_blocks   = WP_Block_Type_Registry::get_instance()->get_all_registered();
        $disallowed_block_types = array_keys( $registered_blocks );
    }

    // Create a new array for the allowed blocks.
    $filtered_blocks = array();

    foreach ( $disallowed_block_types as $block ) {

        if ( in_array( $block, $allowed_blocks, true ) ) {

            // If it's not disallowed, add it to the filtered list.
            $filtered_blocks[] = $block;
        }
    }

    // Return the filtered list of allowed blocks
    return $filtered_blocks;
}

add_filter( 'allowed_block_types_all', 'king_disallow_block_types', 10, 2 );