Q: Is Apple going to fix Safari's incredible slowness?

My copy is fast.

So I have nothing for Apple to fix

There's nothing wrong with Safari. Perhaps you picked up some adware. Try running MalwareBytes. It was developed by one of our own colleagues here in ASC. It gets rave reviews and is about the most proven anti-malware software for Mac.

Hi..

Safari is fast here...

Slowness can be due to outdated software.

Open the App Store then select Updates from the menu top of the App Store window.

If no updates are available, the problem could be caused by a Safari extension of third party plug-in. It's easy to troubleshoot.

Help here > If Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support

And it could just be your network connection or anything between you and the server you re trying to reach including the server speed itself.  For example, after upgrading to 40 Mbps from 1 Mbps I notice no real difference in speed of rendering of the ASC pages.

First, never use any kind of "anti-virus" or "anti-malware" software on a Mac. That's how you cause problems, not how you solve them.

Please test the speed of your connection on this site.

Then start up in Recovery mode. In the OS X Utilities screen, select Get Help Online. A clean copy of Safari will launch. No plugins, such as Flash, will be available. Test again.

Restart as usual and post the results of both tests.

Try a restart.

Do a backup, using either Time Machine or a cloning program, to ensure files/data can be recovered. Two backups are better than one.

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later.

Isolating an issue by using another user account

If the problem is still there, try booting into the Safe Mode using your normal account.  Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer. For each disable/delete, you will need to restart if you don't do them all at once.

Safe Mode - About El Capitan

Safe Mode Startup – El Capitan.