Between my clients' websites and my own sites, the two biggest issues that are reducing page load speed in 2018 are Google Adsense Ads and Google Analytics code. It is not just the Javascript code. Some of the ads that Google Adsense allows includes images of over 100kb in size or worse.
You can disable most video ads and certain types of large sized interactive image ads from appearing in the ads, but I still get large sized images showing up every day and even some video ads every now and again.
There is surprisingly little information on the web about how to tackle this problem in 2018. The Google Adsense ads have all been available in asynchronous form for many years now, and a majority of the advice I read says to use asynchronous ads to resolve your problem. Does not solve the problem for sure.
Very strange that Google is keen to add webpage load speed as an SEO factor, but the two biggest culprits are its own doing.
