Remove Gutenberg Block Library CSS

Paste code to function.php in Child theme

//Remove Gutenberg Block Library CSS from loading on the frontend

function smartwp_remove_wp_block_library_css(){
 wp_dequeue_style( 'wp-block-library' );
 wp_dequeue_style( 'wp-block-library-theme' );
}
add_action( 'wp_enqueue_scripts', 'smartwp_remove_wp_block_library_css' );