shared_ptr is fairly understandable at-least from an application developers usage point of view. std::remove_extent is only used for template metaprogramming a

shared_ptr is fairly understandable at-least from an application developers usage point of view. std::remove_extent is only used for template metaprogramming and generally in linear algebra libraries. polymorphic_allocator is an expert facility. Apart from shared_ptr, the other two are for very specialised purposes - 99.9999% of all C++ code ever written will never have them. But if you need them, you can leverage them. I came from high level languages (JS/Java) and I found modern C++ pretty good - wow I can code native!. I found writing in plain C very difficult and laborious. I found Rust conceptually far more difficult than C++. Also you can't take your traditional data structures and write them in Rust. You have to do it the special Rust way, which makes it a plain when you are just trying to follow the code/pseudocode in a paper. Admittedly, the Rust compiler catches pretty much everything you do wrong. But I code C++ with all warnings treated as errors along with static code analysers and they catch all my mistakes too.