You're right there are other ways too, to change the pace, this time they went with that one. That being said, I'm pretty sure Eden normal raids had adds. Not sure of EW as I barely participated in it. Bad storywroting really grated me there. In any case adds tend to either be meaningless, or if actually meaningful require coordination between tanks, which is often left to be a purview of savage, ironically much for the reasons people here are against, the normals are attempted to be made easy enough for people to pass with minimal communication need.
As for your latter point, you don't get why the memory game is more fun than some other way to solve things. I actually found it rather to my liking. Memorising things kike that is what I consider fun. You like the math boss and I'm sure you know some people loathe it. Not everything can please everyone. This time we got this set of mechanics. That's just how it is.