Writing correct C is REALLY hard and slow (strings, manual memory management, concurrency pitfalls). So the investment is not paying off unless you are writing highly performance critical backend services.

What can pay-off is learning to read C. Node.js, Firefox, Postgres, Linux are all written in C/C++ so if you ever want to really understand what's going on or have to debug a nasty bug, then you will need to be able to find your way around these code-bases.