Hmm I've always thought of C in terms of "portable assembly". Not so much that features were omitted because they weren't performant enough, but because they strayed too far away from machine-primitive operations.
C itself is pretty far from the machine, too, except by accident.
We knew about many of these features then, when C was created - but it wasn't until the 2000's really where computing horsepower caught up to be able to use them in a universal way.