I am a designer and I've been registered recently, but I had enough time on this platform to understand how everything works. (more than 6 months)
It is a total scam for professional designers. They keep the best designers and the most creative ones to entry level and they let mid and top level copy and steal the concepts from the first ones. I have experienced more than 3 times this kind of modern scamming. They take my concepts, modify the design slightly so they would give the same exact response at the end (that the overall look is different and the concept is common so they didn't steal it from me) and let the amateurs win. Ironically nobody thought of that exact idea before I submitted it. Most of the designers have 0 creativity so they go on by stealing other people's ideas. Even in a blind contest I was scammed. The client himself showed my concepts to another designer and he mixed them and won the contest at the end. I noticed from the usage of the same exact font and color palette, which is totally impossible in blind contests where nobody can see what I've submitted, unless the client sends my work to them (or the platform does in this case).
I would not recommend this platform for professional designers, and the clients have been unsatisfied more and more because all the best designers have left this platform. I will probably be gone too, very soon. Even when the winner has not copied the design from other contestants, they copy it from the internet and the clients end up paying $400 for a $5 logo or even worse (someone won, in one of the contests I participated, using a free logo from freepik.com and he just outlined it). Pretty unbelievable, but it happened!
I wrote this and wanted to be 100% honest because I would have wanted to read this before I registered to that awful workplace.