JRiver MC needs some kind of computer to run on. A Mac mini, a windows box, or a Linux box. Your WD Mycloud has a tiny little bit of computer in it, but MC won't run on it. So it's just a networked hard drive for this purpose. You could use a tiny little linux box for this, like a Raspberry Pi. But that requires quite a bit of effort to do it yourself.
The Id that Jim mentioned in a raspberry pi distribution that JRiver makes. It is supposed to do everything for you. Just plug the card into the Raspberry Pi and configure it. I have never used one and have only read some forum stuff about them. I'm not sure how much effort is involved in setting up a JRiver Id.
If the mini works for you, I would keep using it so you don't have to re-engineer anything. Unless you are looking for something different that your current setup doesn't do. Or you otherwise want to switch things around.
Brian.