There are times when we do not need both Classic and Gutenberg editor in a complete WordPress website. In my case, the whole WordPress website depends solely on Advanced Custom Fields plugin.
This approach is to reduce the page load, for example, when we have loads of ACF fields with loads of data, and to show only meta boxes that contain all the ACF fields we’ve created.
To do this, write a custom function in your theme like below:
add_filter( 'use_block_editor_for_post', '__return_false' );
// Remove the editor
add_action( 'init', function () {
remove_post_type_support( 'post', 'editor' );
remove_post_type_support( 'page', 'editor' );
} );
And hook into your functions.php file. Go edit a page or post and you will see no editor anymore.