You can also ignore the people who ignore the complexity of web apps. Classic C programs are very often much simpler than full web apps IMHO.
If you are so inclined, I'd look into how to write your own home-grown version of Objective-C—given that valid C is valid Objective-C.
Because then you would learn Smalltalk and the whole ladder of it all! Smalltalk is far and away one of the greatest joys on programming. :) http://objective.st
The "Gang of Four" explains the patterns in Smalltalk and in terms of entrepreneurship—Patrick Collison's first startup was written in Smalltalk and I think early introduction to it leads to the clean design and success you see coming from Stripe.
https://en.cppreference.com/w/cpp/types/remove_extent https://en.cppreference.com/w/cpp/memory/shared_ptr https://en.cppreference.com/w/cpp/memory/polymorphic_allocat...
I think the basics that are similar to other languages (data types, basic pointers, basic references, classes and OOP) are indeed easy to learn as they are basically the same in most programming languages, but the more specific memory management and weird syntax around some standard libraries make it harder to learn, use and read. Let's be hoest, correct C++ code usually looks ugly and verbose.
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.
Can you recommend any literature?
Undefined Behaviour: Stuff like this - https://twitter.com/jfbastien/status/1280709082626666498