every time you try to create such 'obvious' rules you will break something for someone. And unless the rules are easy enough for that person (or their sysadmin) to understand and modify, all that will happen is that they will learn that the way to make their system work is to disable SELinux, and they will.
This is what is routinely happening with SELinux today, even for professional sysadmins and security people.
getting this stuff right is hard, significantly harder than isolating systems from each other.
it gets even worse, because what you want isn't the binary 'communication via this port/access to this file is allowed or blocked', what you really want is 'you are allowed to do these types of things'. On the firewall side the retreat away from proxy firewalls to packet filters is a wonderful win for the manufacturers of packet filters, but a huge loss for everyone else. things are a little better on the SELinux side (they separate read/write/execute) but there's no control over what they read/write to a file, and you don't know what the impact is of a write unless you understand how every other program that reads the file interprets it.