Rex should not have fine bone. They are a 4 class commercial breed.
Wide feet means better bone, which makes a better Rex. Interestingly, denser fur is something that tends to tag along with wider feet and better bone. I start looking at feet as soon as the kits are born. The long narrow footed ones are auto culls.
The struggle is real, but there are plenty of good specimens within the breed that have good bone and good feet. This is a trait that has often been ignored because Rex were so rare in past years. Now, not so much, so cull it, and replace it.