Don't take those jobs if you want to be hireable I guess? You'd have to be joking to think a HackerRank quiz is going to help you glean any information about their expertise. Such expertise, by the way, is something I'd like to know about. Figure out a way to talk about it. Tell me the situation (you can't disclose real details) and then tell me about a hypothetical project with similar parameters in a way that doesn't break your contract. Or make up an imaginary project -- if you're actually a good programmer you can come up with something that sheds light on your technical ability and understanding.
> Further, there are _tons_ of very good engineers that cannot do 'a bit of show and tell' easily.
I'm sorry, soft skills are essential at my imaginary company. You need to be able to explain your thinking at an abstract level. I don't care if you can't do whiteboard problems, I get that - I can't either - but you do have to be able to walk through problems with other people. Especially problems that you know and understand well. If it's the interview environment that's the problem, well I'd like to informalize that process as well too so people don't feel so nervous about the whole thing. But if you can't explain a problem to somebody 1 on 1 then you'll probably be a very annoying person to work with.
> Doing the process you outline will optimize for talkers
It would optimize for "explainers", not "talkers". Talkers are usually people who can't explain something, and they're fairly easy to weed out from the people who actually know their stuff.