Hello @egoruk
Yes, I agree that most sites are linking to youtube FB, etc.
However, on the contrary, those external resources can slow your website significantly. When the website loads it also needs to load those external resources so the user will be able to see them. This reduces the website load time. I am simply referring to what GtMetrix suggests. If you see the test results, you need to Serve resources from a consistent URL(It’s important to serve a resource from a unique URL, to eliminate duplicate download bytes and additional RTTs.), Leverage browser caching (those resources are coming from external server and cannot be handled on your server by W3 Total Cache), Minimize request size (also coming from external server, youtube), Specify a cache validator (google maps, also external resource).
And when you check the Waterfall, you can see which resources are taking the most time to load. In your case, those are coming from youtube and Google fonts. Please check the screenshot.
This being said, W3 Total Cache or any other plugin, cannot handle those resources.
Please consider changing your review if convenient.
Thank you!