Those are general tips for everyone. If your site is rather new and running on a new webserver as a fairly updated apache or nginx, then this is not a true statement from google pagespeed anymore, since you will already run http/2, which pushes these assets to the receivers.
Most of these tests are for general public and not for your site specific, so it might be that this is more about fixing http/2 and caching and http2-server-push, that will be the thing that speeds up the most.