So then what happens to the unhygienic used shoes after the next person has got them (and hopefully not some odd foot infection) and then uses them up to the point where they are no longer wearable? And what happened to the not so good to unwearable used shoes that the useable ones were picked from?

If the answer is just dump them somewhere, then we are right back to where we started, in the mist of a plastic pollution catastrophe. Except, we moved the problem to poorer countries, that have even less resources and technology to deal with it.