If you read my @Upwork profile https://www.upwork.com/freelancers/~0115a52654d3cda29a, you'll see the last client left a scathing comment but the part you don't see is why I left the site.
There are many reasons, here are the main reasons:-
I got tired of writing the same bio information 30 times a month, in the desperate hope of getting some work.
On average the work rate was ONE reply to every 20 requests for work and ONE job for every 30 requests. The two are not linked as many of the replies were rejections. That was the average, the reality was closer to 1:30 and 1:40, meaning I wasn't even getting a job a month before the lady left her comment - which was a fair comment - I wish she'd given my reasons rather than just slamming me.
The site is run by Asian for Asians and I couldn't compete with their cheap rates.
Despite having passed more tests, being cheaper than the majority and having a larger work portfolio than most of my rivals, it didn't matter.
The money was good while it lasted but in the end the work rate wasn't worth staying on the site. The total lack of politeness on the site was also a factor in my decision to leave. Many times I would check on a request after several days to find what was happening to find at best the possible client hadn't even bothered to check my proposal and on many occasions, despite saying they'd give me the job; they gave it to someone else without even telling me.