What particularly is lacking in iOS itself that would prevent anyone from developing a functioning cloud/remote sync app? Working with the filesystem was very

What particularly is lacking in iOS itself that would prevent anyone from developing a functioning cloud/remote sync app? Working with the filesystem was very tricky in the past but this is no longer the case with https://developer.apple.com/documentation/fileprovider https://developer.apple.com/documentation/fileprovider for the past 4-5 years.