ToO,
I believe Mr Lewis was employing irony in his descriptions of the Scrubbs. They may think themselves modern, hip, with it, the cat's pajamas, cool, and jolly well the best thing since sliced bread, BUT the results of all their refusal of the old order is EUSTACE! Who'd want to be like him before the change? None of us I am sure, but there are persons who think Eustace really the pinnacle of human development. If everyone were like the Scrubbs, what a wonderful world it would be! (according to their way of thinking). They are rather Dursley-ish, don't you think? And who would want to be like that? Or, think of it this way, Eustace is the seed (as are his parents) and Dudley is the final product (as are his parents).
See what I think Mr. Lewis was getting at? I think the Mormon reference a red herring, for there are plenty of people not religious at all who will tell you what you should eat or drink and how much of each because THEY KNOW WHAT IS BEST FOR YOU and you cannot be trusted to do it properly. These are known as social planners and engineers, the mavens of fashion, etc. In their rigidity and unbendingness they probably wear back braces to improve their posture (and think everyone else should too, by gum!). Poor Eustace! He had parents like this! Do you think he had ever been swimming in a lake or river or the ocean? I doubt it! Chlorinated pools for him and regimented laps! No splashing or waterfights or horsing around.
And, to make matters worse, Eustace had never had a chance to develop any part of himself except the "scientifically socially correct" side. He had never read of knights and deeds of derring-do, os sacrifice for a cause, of winning a lady's praise! He didn't know one could act other than for oneself always under the guise of "we know what's best for you" and end up in Experiment House.
I like Eustace myself. He gives me hope that any materialist can discover the greater reality than science can describe and quantify, but not explain - the worlds above us and below us - the One in Whom we live and move and have our being (as St Paul described it).