Regarding k vs j, I will just say that ngn and I both agree that both the k and j array models are far more coherent than bqn. And that k is slow for multidimensional arrays ('mangle your data so it's fast in lists' is a poor response). And leave it at that :)

C is a historical accident. Its existence makes sense in context. Its continued usage only makes sense in context of artificial social factors. There is no reason why we cannot write all software in high-level languages except perhaps when targeting microcontrollers. (For example, there are strategies that can be employed to reduce the rate of memory errors in general-purpose code written in languages without automatic memory management, but there is not much reason to learn these strategies when pretty much the only code that really has to be written without automatic memory management is the memory management code itself, which is hardly 'general purpose'.) The extent to which it makes sense for people to understand the low-level details of the machine is a separate issue I won't express an opinion on here.