Limitize WordPress default scheduled events.

limit-cront.php

<?php
add_filter( 'schedule_event', 'limit_cron_events' );

if ( ! funciton_exists( 'limit_cron_events' ) ) {
	/**
	 * Limitize WordPress default scheduled tasks
	 * https://codex.wordpress.org/Plugin_API/Filter_Reference/schedule_event
	 *
	 * @param object $event event being scheduled
	 * @return void
	 */
	function limit_cron_events( $event ) {
		$array_allowed_cron_hooks = [ 'publish_future_posts' ];
		if ( ! in_array( $event->hook, $array_allowed_cron_hooks ) ) {
			return false;
		}
		return $event;
	}
}