You should always use a loopback IP as the router ID.
Other vendors' routers will use loopback interface addresses (and choose the highest IP in Cisco's case) before they use interface addresses.
In Mikrotik's case, there's no such thing as a true loopback interface. We generally make a bridge interface, name it "loop" or "loopback" or something like that as a way to know what its purpose is, and use that as a surrogate loopback interface. The difference is that this is no different to the Mikrotik from any other bridge interface, so Mikrotik's going to choose the (apparently) lowest IP on the system.
In Mikrotik, it's good practice to specify the router ID explicitly in OSPF, BGP, MPLS, etc, and to use a loop IP for this.
When given a spoon,
you should not cling to your fork.
The soup will get cold.