Many times when someone says "X-lang", they actually mean the entire ecosystem, practices, third party libraries… And for anything popular enough it is indeed impossible to be an expert in all of that. With C++ that’s still the case even if "C++" only means the language itself.

I’ll concede that C with the insane breadth and (over)reach of UB, is closer to C++ than I would like. And that’s a problem too.

I don’t know Go well enough to judge.

We can start with level 1 questions, "name which version where this feature came to be".

Okay, you could… and if you’re honest enough to accept answers like "it’s over 20 years old" I guess any expert could answer that. My main point remains though: if even Stroustrup or Stutter can’t answer 95%+ questions of this kind, it would show beyond a doubt that C++’s complexity got completely out of hand.

Even Stroustrup’s humble bragging about being a "7" at C++ looks real bad. If I’m not a 10 at a language I created and maintained my whole life, I’ve birthed a monster.

My example question was actually in regards to Go, made public in 2009, with 14 years of history.

The bonus round of the same question would be, "name one feature that was removed before 1.0".

We could make this question even more fun, if taking into account gccgo specific extensions, or runtime changes as well.

To put it bluntly, if someone shows up calling themselves an expert, I expect World Cup skills towards the language they are an expert on, across all levels.

While it may not be strictly correct semantically, I'd expect most people to understand "Go expert" as "expert Go programmer", not as some sort of Go historian.