Re: it being an imbalanced marketplace in favor of customers, I guess you’d also say the same about eBay?
I understand your motive is driven to compete with Upwork, but it’s the most built-out and legitimate platform out there, and given their size, I trust them over some smaller operation.
P.S.: I read the OP’s naive writeup. He didn’t follow the platform rules and was surprised that it went against him. Shocking. $400 is a lesson to do more research next time.