You are correct that not everyone needs to know everything, however, the base level domain knowledge to be effective beyond a junior role is very significant for any core role of a company building advanced technology.
You’re not going to become an effective senior software developer at AMD without understanding how their processor architecture design process works. You’re not going to be a significant contributor at OpenAI, unless you have a deep understanding of how their research, training and/or inference systems work. You’re not going to be particularly useful at RenTech unless you understand the right combination of maths, CS, finance, system architecture, and how they specifically use it.