A lack of understanding is not a difference of opinion.
And here I was giving you the benefit of the doubt and hoping that maybe your condescension was unintentional.
There's no failure to understand on my part. Whether you agree or not, the simple fact is that the very restrictions that make iOS so smooth, secure, and easy to use, such as a lack of a file system and sandboxed app environments, make it an unsuitable replacement for OS X or Windows for many users. This is not a "myth" and I am not trolling, as you suggest. I'm not even complaining. The iPad Pro may not be my cup of tea, but I see why others might love it, and I really enjoy the iOS devices that I own.
You asked, "Why would I EVER want a "file management system" instead of iCloud Drive/Dropbox? Any App has the ability to Open from or Save to any of these cloud based file systems."
Well, I can't speak for YOU but nor do you speak for everyone. I personally would prefer a local file system in addition to cloud based third party ones that require a subscription fee for if you want more than 5GB (iCloud) or 3GB (Dropbox) of storage. I also don't necessarily want all my files on the cloud. The fact of the matter is that iOS restricts local file management far more than any other consumer OS. It doesn't even allow you to use your homescreen as a true desktop where you can download or place files, only apps. What part of this is a "myth", a "lack of understanding", or "trolling" on my part? I really want to know, because it could help me get even more out of my iOS devices if I'm missing something here.