Do you want to completely disable Gutenberg on your WordPress website?
Add this code in your child theme functions.php
add_filter('use_block_editor_for_post', '__return_false');
function eos_dequeue_gutenberg() {
wp_dequeue_style( 'wp-core-blocks' );
wp_dequeue_style( 'wp-block-library' );
wp_deregister_style( 'wp-core-blocks' );
wp_deregister_style( 'wp-block-library' );
}
add_action( 'wp_print_styles', 'eos_dequeue_gutenberg' );
If you don’t have a child theme, use the Plugin Builder
That’s it!