02
What you are really buying from a marketplace
A marketplace sells distribution: people who were not looking for you specifically and found a table. That is a real service and it is worth paying for. What is not worth paying for is the same fee on the guest who typed your name into a search box, clicked your own website and booked there.
A venue can have both. Keep the marketplace for discovery if it brings you covers, take your direct bookings on your own site, and stop paying a percentage on the half of the book that was always yours.