These types of platforms have one single function - to drive down the cost and quality of delivered software. I may end up inadvertently using a piece of software as a client of a company that cheaped out and purchased a deliverable from platforms like this and it will end up being a crap experience.
If we had something like an engineering oath and certification that developers had to complete before they could work on any projects, we could make avoiding all these freelancer platforms part of that certification process. Would eventually kill these platforms off, and good riddance.