Like many others I've had an impossibly slow Acrobat DC and Acrobat Reader (latest versions) on a Mac at work. I'm using Mac OS 10.14.6 (Mojave).
I have solved the problem (temporarily?) by opening the Adobe Acrobat application icon (by right clicking on the icon and clicking 'Show Package Contents'). Once in the folder marked 'Contents' I have opened the folder marked 'Plugins', and then disabled the Folder named 'Accessibility.acroplugin'. How have I disabled this? Simply by renaming it (I just put a 'x' in front of the name, so that it reads xAccessibility.acroplugin). It doesn't matter what you rename it.
And hey presto, Acrobat now runs like streaked lightining. I haven't been using it long enough to find out what important things might have been disabled with the Accessibility plugin. So far, no problems with anything. Perhaps someone at Adobe can advise?
Hope this helped someone. Like many, I was getting super-frustrated at this.