I was literally blackmailed by an Upwork contractor who refused to release the already paid-for source code unless I gave them a 5-star rating. I notified the platform and they didn't care - and the solution was for the platform to prevent my ability to leave a review at all, making the contractor happy.
That contractor/agency was still on the platform at least a year after it happened.
All of the writers but 1 were amazing from the start. I had a single bad experience that eventually I made a good experience by just communicating with the writer, telling them I knew they were better than the quality they provided, and to just give it another go. That story eventually became one of my favorites[2].
I hired from all over the world to get different viewpoints, and my prompts were usually very open. It would be something like: An historic fiction set in your country's or region's capitol city during a war.
And I would have 5 openings for stories similar to that.
Generally, had very positive experiences with Upwork and other platforms including Freelancer.com which I no longer use anymore.
Doesn't the rating part come after the contract is closed?