It's hard to say for sure without knowing his whole situation, but I will agree with you that when I hear someone say they've submitted 750 applications, my first thought is that they're taking a machine gun approach, applying to a lot of jobs in a short time. I was always taught that you tailor your resume to the position you're applying for, and apply only after doing a lot of research on the company to know whether you are suitable for their position. I'm older than the author of this post, and applied for my most recent job at about his age—though it was a few years ago, before AI was really a consideration. In my entire life, I've probably applied to ~25 positions, made it to the final round 8 times, and been hired 6 times.

Knock on wood that he's wrong about the cause of his current frustration, because that means it's fixable.