One simple way would be require video submission where you have to speak your name and mention that you have joined upwork as a freelancer. But then upwork would have to spend more money on validations. They probably don't care as much.

I sometimes hire from upwork. My litmus test is simple. I want to talk to you for 5-10 mins on video. If you cannot show up or have issues doing a video meeting, I won't proceed. It may help getting rid of scammers who are hiding behind a fake profile. I remember one guy telling me that he has speech issues and can only "interact" through messages/email. Even if true, I cannot trust someone on the internet like that.