On Mac I just open the iCloud folder and the files are there, just like Dropbox
On iPhone I open the iCloud Drive app and the files are there just like on Mac, much like in Dropbox pp expect Dropbox uses list format.
Personally I like iCloud currently more, but as you said it only works in Apple ecosystem (which I'm currently fine with). Recently I also setup OwnCloud on my RPi and it seems to fill my niche usage just fine as well, but I still don't quite trust it.