Neither knowing C nor knowing the lower-level details of implementation hurt you — in themselves. What can and will hurt you is if you consistently think and work in terms of the low-level details, even when it’s inappropriate.
The old saying was that “real programmers can write FORTRAN in any language.” If you do the same using C, it’s not an improvement. If you’re writing Lisp, write Lisp. If you’re writing Python, write Python. What’s appropriate and reasonable for C is not for either of those (or any of many others).
A great programmer needs to be able to think at many different levels of abstraction, and (more importantly) recognize and apply the level of abstraction that’s appropriate to the task at hand.
Knowledge of C’s level of abstraction doesn’t hurt. Ignorance of alternatives can (and will).