WriterAccess has a lot of writers working for them. Some are quite good

Writer Access provides access to already vetted writers and handles all the stressful elements from finding writers, providing briefs, tracking progress and handling quick and fair payments

Two things I like best: 1) direct access to the writers. It's more of a collaboration, and we can post questions and answers back and forth to make sure the piece is on point. 2) the platform has features others don't. The ability to save briefs, profiles, set up folders, segment different writing teams. It's a very intuitive and robust system. I love how you can see which writers have been active, can see their projects per month rate.