In my world (see other reply), I get to deal with whatever is in dozens of codebases written in many times and places. The superset of everything they're using is pretty much everything.

Beyond that, even the "good" modern subset of C++ is crazy complex. I've sat in a room with some of the better C++ programmers in the world while they study and try to comprehend the new features like rabbis interpreting the Talmud.

If there's one concise, fundamental rule of software engineering, it's this: Complexity kills.