To setup port forwarding you have to understand how to configure the firewall, yes. This is both a drawback for simple use cases but a boon for more advanced ones. It cuts both ways. Personally I think it’s rather unfair to call the UI unintelligible. If you don't like it just ssh to it and configure it that way. Everything you can do is packaged up in a nice command structure.
I've managed cisco amd juniper routers. And I can't make heads nor tails of it.
As soon as you wonder off the default track, you're expected to understand deep level networking terminology abstracted in a UI tailored for experts.