If there is one guiding philosophy that C++ has it's abstraction without runtime cost.
The (implied) corollary is that compile time cost, mental cost and social cost of language features do not matter.
As long as there is at least one person on the planet who really understands the ins and outs of a language feature, that is sufficient proof of the language being simple enough. There is no need for anyone to understand the entire language.
That's fair but Rust has the same primary design goal and yet I find programming in it more ergonomic (despite Rust having a cranky borrow-checker that C++ lacks).
I don't know how much of that is due to C++'s historical baggage and how much is due to a greater concern for usability and elegance on the Rust side, with consequent discretion when adding new features. But I don't think it's entirely the former.
The (implied) corollary is that compile time cost, mental cost and social cost of language features do not matter.
As long as there is at least one person on the planet who really understands the ins and outs of a language feature, that is sufficient proof of the language being simple enough. There is no need for anyone to understand the entire language.