Why is this important?
To give some context, if you want a URL to load within 5 seconds on a fast 3G connection (~ 1.6 Mbps), you have about 1000KB budget for ALL of your content.
What does the Hint check?
How do you resolve this issue?
Moving beyond spot fixes, you should seek to build pages with a performance budget in mind, for each of the page templates you will require. Check the resource URLs below for inspiration.