Being an expert at assembly probably means you're an expert in low level programming. We still have a need for those people, because they'll probably also be able to write C/C++/Rust/Zig/etc very competently.
I consider myself pretty competent in C(And C++ to some degree), and I have a pretty good understanding of how computers work on a lower level, but if you ask me to write React UI components, I probably wouldn't fare well. I understand Javascript/Typescript, sure, but I'm just not familiar with the best practices of modern day frontend engineering.
C is a language that is able to target basically every platform under the sun. It's versatile: User-space applications, kernel modules, and embedded firmware applications with an RTOS or even running on bare metal.
LLMs can produce basic C code, but (still) struggle with more specialized tasks.
They can be incredibly useful for skimming through long datasheet PDFs, but it's still up to the engineer to actually make sure the code it produces is actually good.
And for how many more months will this state last?