IMO, if c++/cfront didn't ride on the tails of c, I'm skeptical it would've seen widespread use, but then, that's its main identity which limited it in ways that C++ was not willing to change; It is highly irritating to spend as much time to sanitize the implementation with Coverity/Valgrind and the ilk when the compiler could've handled it.
With C++98, Bjarne's book on c++ internals could've give you good insight into what went on, but later it turned into a whole cottage industry of "effective, more effective, proficient, performant, c++" series of books -- so kiss goodbye to any notion of being able comprehend existing code that's not written by you (until llms arrived). I'm happy to have spent time to learn problem domain instead.
I'll still watch the documentary since it has some of my favorite folks (Kernighan, Stepanov).