WPEngine support said the theme itself it causing a massive delay.
Text from their support “I did setup a tool we have to trace php processes on the site and I am seeing that there is a custom process, i believe from your theme, that is getting called lot on each page load which is adding 2-3 seconds to the page load. The function is “Composer\Autoload\includeFile”, here is the overview of the trace i got: https://s3.amazonaws.com/wpe-screenshots-jc/screenshots/2021-06-23_10-47-06.png”
Any way to speed this up or otherwise prevent page load delays?
