Remove taxonomies that you probably won't need, and take forever to load all the terms in ACF taxonomy field.

functions.php

<?php

/**
 * Remove taxonomies that you probably won't need, and take forever to load all the terms in ACF taxonomy field.
 *
 * @version  1.0.0
 * @author   @JiveDig
 * @uses     Advanced Custom Fields
 *
 * @param    array  $taxonomies  The existing taxonomies.
 * @param    array  $args        An array of args used in the get_taxonomies() function.
 *
 * @return   array  The modified array of taxonomy names.
 */
add_filter( 'acf/get_taxonomies', function( $taxonomies, $args ) {

	// Array of taxonomies to remove.
	$remove = array(
		'post_tag',
		'post_format',
		'yst_prominent_words',
	);

	// Loop through em.
	foreach ( $remove as $taxonomy ) {
		// Remove them from the options.
		$taxonomies = array_diff( $taxonomies, array( $taxonomy ) );
	}

	return $taxonomies;

}, 10, 2 );