I am not arguing that higher-level languages are worse and that everything should be coded in C. Each problem requires different tools for its solution. And to that end, high-level concepts should be done in a language-agnostic manner.

However, lower-level understanding is paramount. For instance, and most-importantly today, taking advantage of multi-threading requires understanding of cache-coherence, memory-alignments, et cetera.

Therefore, while a proper serial algorithm today may be correct its scalability is going to be limited without lower-level understanding. Although, I'll admit that can be built into the higher-level languages (like concurrency in Clojure for instance), but I personally prefer to understand what is going on rather than blissful ignorance :)