Unable to create a directory for iCloud Photos. Restarting your computer might... (Error 5)

I only have one cloud service, ...Dropbox.

But all my iPhone photos are in iCloud, not Dropbox.  So it is certainly a reasonable expectation to have iCloud for Windows installed on a PC and that has NOTHING to do with OneDrive or Google Drive, or any other cloud solution...   My troubleshooting enabled my to realize what the issue is and its 100% repeatable.  Customers who use OneDrive don't have a problem, so maybe I should leave Dropbox and go to OneDrive.  I'm sure that's not what the CRO at Dropbox would want to hear...

And I completly agree that this is absolutely on Apple to fix, but of course I'd like to have the fine engineering team at Dropbox help solved this issue, work with Apple to update their iCloud for Windows product to detect and recognize the presence of Dropbox cloud services just like it does with Microsoft's OneDrive. 

That is the solution to this issue. 

IMHO, its incumbent upon Dropbox to recognize the issue exists for it's customers even if it isn't caused by DropBox, and get engaged with it's partners to solve it.  Lets also recognize that Dropbox's decision to stop supporting Symlinks (external) is a contributing factor.  Dropbox backup will backup picture and video folders, but it will not allow the sync of those folders across a customer's devices...

So yeah, this is an ongoing issue that need to be addressed.  There is no solution as it stands now, and I'd love for Dropbox to advocate a fix for it's customers.  There is certainly a lot of community support for this issue as it's a very common error for Dropbox customers with iPhones.