Any platform that will allow anyone to bid for jobs will attract bad developers and developers from third-world countries, who are going to bring bid offers down and push away good developers and developers from first-world countries.
Any platform that will allow anyone to post jobs to developers from third-world countries will bring crappy projects posted by amateurs with vague specs.
The more popular it gets, the crappier it becomes. There's no way to win.
PeoplePerHour is better than Upwork, it's mostly people from the UK. There are also services where they screen candidates and only accept the best developers (I signed up but there was too much friction and I lost interest).
In general, IMHO the market for remote devs is there, but I guess most people if they had to spend a lot of money for a dev they'd much rather have him work in the office or at least meet him in person and have him come in every once in a while. What's left is people who will be ok with crappy developers that will do the job for 1/10 of the price, and they might as well give it a shot.