iCloud Drive and sharing have not failed me. On the contrary, they have worked better than I expected. I have kept a lot of data on iCloud, and I have not had any show-stopper problems. I am currently working on a new edition of the Paperless Field Guide. I am running the entire editing workflow through a series of shared iCloud folders, and it has worked exactly as expected. Granted, there is still plenty of work to do with iCloud Drive, but it is working well enough to handle sharing when I am in control of sharing.
The trouble is those instances where I am not in control. For example, I have many clients who have never heard of iCloud Drive and do not own Macs. They have, however, all heard of and installed Dropbox. When you work in a service industry, adopting a technology that requires your clients to change their technology never works. Also, I make three separate podcasts that invite guests who also sometimes do not have access to iCloud. In the end, I am keeping Dropbox—not for myself but for others.David Sparks, I’m Keeping Dropbox
I think that this is one of the main reasons why people need to keep Dropbox in their lives — its sheer ubiquity.
Like David, I'm using iCloud Drive for my documents and photos. But now, instead of having the Dropbox and Google Drive apps hanging around on my computer, I access both of those through the excellent Transmit as required.
I'm also using Transmit to experiment with Backblaze B2 for some projects. More on that another time.