The Dropbox mobile app is filling up my iPhone storage

As I stated, the Dropbox app cache was empty and the files had been completely uploaded.  On an iPhone, the Dropbox app cache is emptied via the Dropbox app not via iOS itself.  Deleting the Dropbox app (including all of the app's documents and data) and then reinstalling the Dropbox app did clear the Camera Uploads folder - but as I stated, this is just a very crude, temporary hack since the problem remains: photos uploaded from an iPhone to Dropbox reside not only on the Dropbox cloud but also in the iPhone's Dropbox storage (in addition to in the iPhone's photo storage until permanently deleted).  Deleting the photos in the iPhone's Dropbox storage also deletes the copies in the Dropbox cloud.  Unlike on my Windows laptop, on my iPhone I cannot find a method for marking all of the Dropbox folders as online only (and for making the default online only).

I don't want the files and folders synced from the cloud to my iPhone!  (Perhaps in the future I'd want to sync selected files, but for now I'm happy to keep selected copies in my iPhone Photo Gallery rather than having "copies" in the Dropbox app that aren't really copies but still take up iPhone storage.)  Dropbox is not very useful on an iPhone if I have to reinstall the Dropbox app every time I need to clear space.