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Boot stiffness is a property used for foot support, it is best employed for a person walking long distances over undulating terrain carrying heavy loads. The sole stiffness is not about adding grip.
Camping gear has been getting lighter and lighter over the last decades leading to the decline in the need for a stiff boot for the average hiker walking on trails carrying low weight. Boots and stiff boots included do have their uses.
Vibram is certainly not limited to stiff soles btw, there is a whole world of more barefoot oriented designs you might want to look into op if grip and feel matter most to you