It is not worth learning assembly.
You are dead wrong. I wish I had the points to downvote your post.
You are correct that its not worth learning assembly, in order to learn "modern" software development.
What makes learning assembly valuable is that it is the most barebone, lowest level set of instructions that a human can cobble together for a CPU to execute. Every other language involves cobbling together hundreds of CPU instructions which would be magnitudes more inefficient than expressing it in assembler. Because higher level languages are designed for humans to understand what they are instructing the CPU to do, in the desire to increase the output of human programmers, at the expense of actual execution efficiency.
By writing programs in assembler, particularly I/O routines, the human programmer learns how the CPU "thinks". And indirectly, learns to comprehend that all current computers are constructed to the same design specified by Turing back in the beginning. You come to realize that all CPUs work the same way, even though they have different sets of CPU instructions. They're all moving data from storage to memory, memory to register, simple ALU operations in the register, and moving it back to memory and eventually storage.
Most people cannot read a book, and magically implement code or concepts from scratch. They need to write programs, have those programs fail, and learn to figure out why they failed. That way, those programmers learn how to express what they want done to the machine. Learning assembler is learning how the CPU thinks, and how assembler instructions are building blocks to abstractions. Assembler programmers (and to a lesser extent C programmers) really do understand "what the machine is doing".
Yes, once you can master assembler for one CPU platform, you'll probably never need to learn to do it for a different CPU, and probably never need to write assembler again. You learn to code assembler to truly grasp how a set of chips operate to produce the simulacrum that is the personal computer.