iCloud Drive is a cloud storage competitor that Files works well with, but Files also supports Dropbox and Google Drive and many other storage competitors (anyone who wants to implement the API gets to be in Files). Also, the argument that Files is somehow replacing Dropbox doesn’t even make sense because you need to have the Dropbox app installed in order to connect Files to Dropbox. It’s not a standalone integration, it depends on third party apps providing the correct extension to work correctly.
It’s surprising, to me at least, that everyone accepted Files coming packaged with every new iPhone and iPad sold, but for some reason its position in the App Store is a controversial topic? How many people even delete Files and search for it again? Not to mention that installing system apps from the App Store doesn’t even install anything, because the app was never removed, just hidden from Springboard.