It'd be nice if programs had to reject through ERAS and at least click a dropdown box that lists primary reason for rejection, like "Insufficient demonstration of interest in program," or "USMLE score below desired range" (just spitballing here). They'd probably all just pick the most generic one and go with that but it's a huge mystery to me as to why I got an invitation from one program vs another.

<< A large aspect of all of this is luck. There are hundreds of amazing applicants and less than 40 interview spots at most programs. Accept that it is really out of your control and nothing specific you could have done (TBH this makes me feel better about all the rejection)< completely agree. It probably also has a lot to do with whether you are a good fit for that program.

or they don't think YOU would rank them highly!

OP here, excellent points. I think I just have to convince myself that there's nothing inherently "wrong" with my application and that ultimately I want to go to a program that wants me there, and not to overthink it past that. x2 << there's nothing wrong with you or your application!