My anecdata as a PhD engineer: my first job out of college came from putting my info into a faceless corporate careers website. I also got a competing offer through LinkedIn. My current job at a little <100 employee company was obtained through a recruiter on LinkedIn. When looking a few months ago I got another offer from a corporate careers website.
I felt pretty useless fresh out of college, but once I got my first job, I started getting messages from recruiters on LinkedIn fairly regularly. I'd be interested in how people do their due diligence in checking the authenticity of LinkedIn recruiters!
As for indeed, when I used it 5 years ago to get my first job out of school, it didn't impress me. I didn't get any leads from it. Zip Recruiter I think is an actual scam.