If wall isn't supposed to carry most of weight, as opposed to sole, why is it that in the old days when some horses' jobs were to walk/trot cobblestone streets, they were shod (so no sole ever touched ground) & worked for decades without a problem?
Lameness, breakdown & early 'retirement' was also common. 'Navicular disease' for eg, has long been recognised as a common problem of domestic horses, especially those worked hard on paved roads. And of course many people, for eg, can smoke heavily for decades without getting lung cancer either, but that doesn't mean smoking is proven safe & right. So I would ask for evidence before jumping to that conclusion for a start, to consider the differences between those horses with *apparently* no problem. The claims that conventional shoes are implicated with some of these 'problems' and egs of horses shod differently being more sound is not a new idea either. Unfortunately there has been little real evidence to go on - one way or the other & I believe there is still so much we don't understand. But from current research into hoof function, as well as countless egs, I do believe peripheral loading is a major factor and should be looked into much more objectively.
FWIW, I don't think there's any evidence either, that horses in various domestic situations should necessarily have feet like a desert mustang, for eg degree of concavity. That doesn't strike me as logical either, let alone the apparently wide held assumption that feral horses all have good, sound feet - ferals can have very different feet in different environments and are not without problems too. But there is so much we have learned, and can learn more, in considering what Mother Nature gave the horse & how it works, & the differences between hooves that function soundly & optimally compared to the 'problem' ones.