Sign me up.  I am joining the club that says DPP4 is pretty much unusable on a MacBook.  I wanted a laptop that was more portable than my 17.5-inch Windows 10 laptop, which does not fit into 99.99% of camera bags.  It needs a bag of its' own.

After a week of trying, DPP4 does not access my Photos, even though I have gone into System Preferences | Security & Privacy, and checked to confirm that Photos allows DPP4 access.  It supposedly does.  Photos just never shows up in the Folder View of DPP4.  

Instead, DPP4 wants to access the folders holding LR and PS images from the Creative Cloud.  I am not able to access my local MacPro HD, either.  But, I can browse application configurations for some odd reason.

I can access network drives, which is where DPP4 totally loses its' marbles.  I do not dare explore my photo archives using the Mac.  I get a colorful spinning beach ball whenever I move the mouse cursor, click on a folder or an image, or just breathe on it for that matter.  Accessing the archives are not a problem with the Windows 10 laptop.  

The archives are setup in 4TB volumes, with one for use with a different camera.  Forget about accessing the 20TB backup archive.  The beach ball comes out, and it is game over for the next several minutes until the spinning beach ball goes away.  Move the mouse, and the beach beach ball comes back for several more minutes.

I am not familiar with MacOS, but I do have 5 decades experience with computers.  In fact, I hate Apple products and this experience only confirms that opinion.  For whatever set of reasons, DPP4 is totally unusable on my MacPro.  I do not see a fix for this.  It is what it is.  You cannot use DPP4 with folders containing more than a handful of files.