By default, Google Maps is selected under Theme Tools > Map Services, which is a contributing factor to slowing down your website. In this case, MyListing performs a dns-prefetch to Google’s API, which is an external lookup, even if you have not configured the Google Maps settings.
This is NOT something specific to Google Maps. If you happen to toggle on MapBox or OpenStreetMap without configuring it, the same outcome would occur.
What’s the Big Deal?
When you prefetch anything on your website, you are telling it to make a DNS lookup for an asset or service that will be needed at some point during a page load. If the DNS lookup is needed, that’s fine, but if not, you’re deprioritizing other parts of your site that actually need that DNS lookup or need to load.
In layman’s terms, we would rather not waste time talking to someone if they aren’t going to help. Instead, we want to ignore them and talk to the people who do want to help.
How to Test
If you want to test your site, you can use this free tool (website) by simply entering your website URL.
add_action( 'wp_enqueue_scripts', function() {
wp_dequeue_script( 'mylisting-google-maps' );
wp_dequeue_script( 'google-maps' );
wp_dequeue_style( 'mylisting-google-maps' );
wp_dequeue_script( 'mylisting-mapbox' );
wp_dequeue_script( 'mapbox-gl' );
wp_dequeue_style( 'mapbox-gl' );
}, 99 );