Rubber is a good insulating product, according to Dr. Christopher, back in his day Japan outlawed such shoes because it would insulate the human from the earth and leather was the choice at the time.
Moccosins made the old way work well if you want something dead around your foot, otherwise I prefer the most light weight sandal you can find and allow the soles to wear out and let your foot touch the earth. I just got 3 years use out of a pair of sandals that cost less than $10, I finally walked out of the sandals because the fronts ripped out. My next pair have a nice hole on the heal and on the front where my foot naturally touches the earth. Wearing such shoes for some time now has made it so I can't stand normal shoes, to put my foot in a normal shoe i like going to jail, it literally is torture and to think, I once wore large heavy steel toed shoes for 30 years in a factory!!! Seems like walking out of 30 years of hell and into the light.