As for the interview problem you face, it's due to offer and demand. I work in an investment bank in Hong Kong, we need ideally super experts in everything who can do low latency, understand swaps, know other brokers, client systems, exchanges, FIX by heart and stuff like that.

We start interviewing on those constraints and then if we find no one we lower the bar until we ask for a LinkedList implementation and find a guy doing it relatively ok. And the guy turns out to be great and useful most of the time and we have to teach him the gaps. If you cant get in the job you want it s prob because they find too many people already and can afford to select on absurd skills.