I don't think the delivery part itself is the main problem, there's no inherent problems with restaurants needing a long term contract with delivery personel/co

I don't think the delivery part itself is the main problem, there's no inherent problems with restaurants needing a long term contract with delivery personel/companies, if they get unfair terms there are no real barriers for them to do their own delivery or go to someone else. However if their delivery isn't easily discoverable then this does hurt them, and unlike with simple delivery there's not too many options to make yourself discoverable when the de facto standard is run by a single company.