Very good analysis, and I do agree with you to an extent.
I don't think that the Chaplin's character in the Great Dictator expected that speech to change anything, it came across as a sudden outburst toward the corrupted moral values he was witnessing around him. If it was presented as a solution then i'd thoroughly agree, but that was a genuine display of human emotions, Chaplin was pure, and you can't possibly fault him for that.
I agree that the intricacies of War can't be dealt with on a whim. to me the challenge lies in our collective values, our dependence to conventional dogma and our reluctance to put ego aside and work toward the betterment of an ideal world for our children to live in. Until there's a drastic paradigm shift in the way we view the structure of society, we will always look to the external (government, religion, ect..) for a sense of security, control and truths at face value because we fear social ostracization, and we underestimate the power of autonomous and rational thinking after being lied to and conditioned for years. Those types of changes don't come overnight, and they certainly don't come in handy when were dealing with Political conflicts, but then again, Political conflicts can be barberic at their core, the result of War can have devastating implications that are in most cases necessary, but it doesn't make the nature of this structure morally right. We are an evolved species in the sense that we cultivated language to communicate with each other, but were still the only Animal that kills for other reasons than survival. I think there should be a harmonious balance between what is necessary for survival, and morally sound convictions.
Chaplin wasn't offering a solution, he was reacting to the madness in the most human way possible. That's what makes it so poignant.
I agree with everything you said to an extent, my problem is that in the context seems more a moral lesson than a pure speech and this problem is what put me off with it. Even if i reckon the intentions of Chaplin are pure, something i will not say for someone like Nolan just to to say the first person that comes to my mind. Specially for the reason i mention before.
I believe that the speech was one of the reasons Chaplin wanted to do the movie, to express his feeling on humans nature and the problems of that time but to me seems more cliche than other thing.
All of this in the context of the movie, i believe the same things.
And on topic
A pedohile/murderer being judge by the mop and the criminals in germany, one of the most amazing secuences ever. This is the most bizarre twist in people discussing about each other morals, Lang was a master and Peter Lorre is certainly underrated.