My list of advantages:
- long-term stability: the code I wrote two decades ago is still valuable to me
- short (!) compilation times: this is a huge productivity boost
- the language is very explicit: one can see and understand what is going on
- mature tooling: good compilers and many other tools
- simplicity and elegance: the language is small and not much I need to remember
- portability: supported on many different systems
- performance: C code can be very performance and usually it is without effort
- lean: there is no bloat anywhere
- interoperability: it can interoperate with everything
- no lock-in: it does not lock you into specific frameworks or ways to do things
- maintained using an open and (relatively) fair process: not controlled by specific companies
- what needs to be done, can be done: there are never showstoppers
I should also talk about disadvantages and which I think are real and which are not, or not serious