What do the cool kids use to write realtime or realtime-ish software with these days? What gets used for firmware? What gets used to write kernels? What gets used when you have to interact with hardware that uses memory mapped registers?

It might be C++ instead of C for some of the above, but that doesn't make C "a legacy tool".

I’m not saying it isn’t used.

I’m saying it’s a legacy tool from the early 70’s that is absolutely terrible compared to what we could have.

Cool kids use it because there is no alternative.

Two words: Buffer overrun