Before I begin, I just want to state that I am not recommending the changes mentioned below as an official guide for fixing Add This load time.
Purpose of writing this post is simply to share what I did about my problem and this should in no way be considered a fix or considered OK to replicate, just an update on what I did.
I noticed my web site would load. How ever the share buttons would take a little while to show up.
I used https://tools.pingdom.com to get some performance data.
On doing some research online I found help on the add this web site here https://www.addthis.com/academy/optimizing-addthis-performance/
What I gathered from the above article was to identify where my code was loading the addthis_widget.js and make it asynchronous, i.e. simply add a async=“async” as an extra item to my script tag.
I then started looking around in the plugin code myself how ever there were many files and I was not sure what file was loading the addthis_widget.js.
Then I installed a very cool WordPress plugin called String Locator what this really does is tell me where in my code a certain string lies. Something very standard in most programming editors. A simple Ctrl+f. I think this plugin is simply spectacular.
On viewing the file wp-content/plugins/addthis/frontend/src/services/addthis.js I saw some code that was building a script element to load the addthis_widget.js
Then to my best programming knowledge, I changed this code to include the asynchronous call, again this should not be tried, just an update on what I did.
I saved the above changes and ran a follow up test on https://tools.pingdom.com