I don't disagree, but I think you'd be surprised at how many would respond in some capacity that was helpful. Even if 100 people refuse and one person doesn't, that's still more information than you had before.
And in my experience, if you fail the technical portion of an interview, most companies will tell you. Meaning, if you ask and they don't bring up technical skills, it's probably not the technical skills.
You can always say, “I know you can’t give me a specific reason on why I’m being rejected, but can you offer any guidance on how I can do better? Anything you can offer could be helpful.”
And in my experience, if you fail the technical portion of an interview, most companies will tell you. Meaning, if you ask and they don't bring up technical skills, it's probably not the technical skills.