Okay, even those of us who love WordPress will admit that this superflexible cms has its drawbacks, and one of them is the load/caching issue. No matter what theme I’m using, the #1 optimization recommendation is always the same: “Leverage browser caching.” Which is always followed closely by “Serve scaled images.”
Ideally, the nice folks at the WP development commune would try to tweak their core files to address these issues, but clearly that’s not gonna happen. So how about some enterprising developer coming up with a plugin, script or SOMETHING that attempts to address (or at least minimize) these shortcomings?
To implement browser caching, all you have to do is edit the .htaccess file.
As for serving scaled images, are you talking about for mobiles? There isn’t a silver bullet yet but adaptive images works rather well at this time and is easy to implement.
Reducing HTTP requests is important, themes that enqueue 5 different css files on a single page are usually bad news.
You just need to tweak that in your Server. Be it Apache (.htaccess) or another kind. (They all have, or should a way to set the expiration date).
Otherwise, you can set it too with PHP headers. Hook to the template_redirect action.