I’m gonna start this post with this graph.
This is the size of the assets each of these Page builders load by default, in KB (CSS + JS files combined). BEFORE ANYTHING ON YOUR SITE IS LOADED.
As you can see, Divi and Elementor (the two most popular page builders) load approximately 1 Megabyte of assets on your page. How are you going to optimise that?
The answer is you cannot. Not easily.
The better to solution is not to use a page builder. Spend a little bit more early on on your website, or factor in a redevelopment to your budget.
If you must use a page builder, use Beaver Builder Pro or Oxygen Builder. These are at least performant and handle the loading of assets properly / on demand depending on your usage.
If your web developer / designer says to use Elementor or Divi, just fire them. Seriously. They do not care about your website or your business and they know nothing about making quality performant websites.