You need to take ownership of the issue, and keep all your shoes out of his reach. If you don't have a closet you can shut them inside of, get a sturdy box - an "underbed box with lid" would do if storage space is an issue and be completely diligent about all shoes going IN the box when they are not on your feet.

Then make sure there are plenty of "okay-to-chew" things around at all times.

He WILL outgrow this eventually, but until then, you need to keep all shoes away from him.

It is boredom - he needs something to do, so get a bunch of cheap chew toys to give him.

When our family St. Bernard Freckles was a pup, when I was a teenager, if I left my closet door open (duh, stoopid me) she would carefully select one shoe to chew - always from a pair that she hadn't chewed yet, of course!