For as many low quality freelancers as their are, there's an equal amount of clients who want the next Facebook and can pay you $250. A site for specialists freelancers/more complex projects would be great, although at that point they're usually called consultants.

So a freelancing site where the minimum project cost starts at like $10k.

I´ve been thinking about working through upwork. What are the downsides to it? It would be good to know before I do anything through them.

Upwork is an entry. Not a journey or destination. It's sort of like a paid internship (but it atleast pays). I recommend to build a portfolio of it but pivot as soon as possible.

I hire for extremely cheap on Upwork but in return for their work, I coach my hires (typically students).

I have the satisfaction of alteast 10 cases who after my projects are able to market and project themselves better and are able to get place in the ~ top 30% (by salary) of their peers.

but after upwork, where do you go? i haven't yet found any online project site that would be any better.

yeah fair question ... I would say you need to learn sales skills, be humble and learn from someone who can teach you ... going the "project site route" isn't particularly optimal IMHO. Contribute to open source, develop some example projects and try to sell yourself. Ask your customers / partners to provide references. The market will adjust sooner or later. I know many people who worked hard, did a good job and reverted to the mean much faster than you would think. Good luck!