If that were true then every javascript coder would need to "understand" every javascript runtime. And every Ruby coder would need to understand C in case their

If that were true then every javascript coder would need to "understand" every javascript runtime. And every Ruby coder would need to understand C in case their libraries break. Every Java programmer would need to know the implementation of their JVM. Every ... In practice when the tools we rely on break, we have other alternatives. We tend to start with web searches and asking questions on SO. We can try different versions or libraries. Most problems have workarounds that may or may not be applicable. Sometimes deep knowledge helps and I will tend to advocate for it. In the case of template metaprogramming, deep knowledge gains you very little and a common breakage will add 2 extra instructions to your runtime execution. If that matters you are already watching for it. As soon as you use COM, RPC, a web API or any scripting language you have already done something that would blow this cost away for an abstraction. Knowing enough to fix a problem doesn't always mean a deep understanding of every library and tool even in C and C++ land. There is simply too much for any 1 person or any dedicated team to know, we must rely on division of labor. That is why we find abstractions like COM, RPC, web APIs and scripting languages worthwhile, they allow someone else to handle some part of our cognitive load at the cost of runtime performance.