There's no need to learn "all the assembly" of a modern processor, just the basic instructions and maybe write a few simple programs to understand what's going on. Even though writing assembly is hardly needed today, being able to read and understand assembly is very valuable for debugging and optimization sessions.
I'm not so sure, I've been thinking about how to implement a fastest 'very small map' (let's say a maximum of 16 key, with the keys being 2 bytes), but for this I need to learn SIMD x86 assembly language :-(
I've found learning assembly a necessary evil for certain work. I use Rust to automate lifting binaries and conduct protocol analysis to find vulnerabilities. Without knowing assembly it may limit the depth of analysis that can be done.