As a League spectator you don't really need to understand the combat to understand the meta. I mean when watching baseball you can't really tell much about a specific pitch, it's just the outcome you care about. Team X killed Team Y, that was good for Team X is enough to care.
Sometimes I find that casters miss a few small but important details in the heat of the moment and get derailed about most obvious topic. Playing the game or at least knowing about the mechanics from having spectated before gives you some analytical predictions. Whether that's to better enjoyment of watching the game is up to you.
