I use HOSTS (that one, in fact), NoScript, and PrefBar (to have control over flash, acrobat, image loading, etc.) and that pretty much strips what I get in my browser down to the minimum to make a given page work. On average my browser loads maybe 10% of what the server would like to send me. (No adblocker required, either.)
But even thus, modern browsers are still slow, nothing to do with the server or devs' finest efforts at optimization; as best I (not a coder but an experienced observer) can tell the problem really is in the browser itself: If you run any of the Mozilla family on a slower machine, you can actually see it doing linear singletasking (most visibly when asked to save several files in a row). Old Netscape didn't have this problem; it arrived with the opensource version. One suspects a plague of bad coding Zen [a la Abrash's Black Book].
And why does it take 100mb of RAM just to display a 10k text-only page?? and up to 1.9GB to run a couple videos? the same HTML renders in any other program at a cost of a couple MB, and flash itself uses very little. My observation is that the problem is mostly in plugin-container.exe, but it's not the whole issue. Disabling disk cache entirely helps too (its current convoluted structure seems to cause a major memory leak -- seriously, 1500+ directories holding one file apiece??), but not enough.
The latest bizarre slowdown (this is in SeaMonkey 2.39, can't run a newer one BECAUSE IT'S TOO DAMN SLOW) is running CPU at 100% for 30+ seconds when asked to merely copy text from a webpage. Thank ghu for the "Copy as Plain Text" add-on, which works around the problem.
Performance gets significantly worse with every update, which is why I've fallen into the practice of using the oldest browser that will still halfway work.
Browser devs need to be restricted to working on old hardware, so they can see what they're doing to the rest of us who can't justify new hardware just so the browser doesn't take forever to do its job.