I've sold ~20 used basketball/running shoes so far this year (and a car), most of them for under $100. I am getting probably a 4:1 (FB:kijiji) sale ratio, and the responses at least 10:1
If you are pricing to sell, whether its vehicle, shoes or clothes, the responses and actual sales are not even comparable.
I never thought FB marketplace was so useful, but the numbers are there and it has the users.
If you're trying to sell some DS sneakers for $200+ i don't know that market or any other overpriced items where you're expecting people to pay what you paid for it, marketplace won't work.