I don't need to write a complex software system to utilise my knowledge about it.
Also, I don't have a CS degree and that's not what I advocate for. I advocate for developers who spend years honing their skills and learning fundamentals of the craft.
Spending years honing skills does not mean wasting time. In fact most self studies do it out of passion, which means a lifetime of honing skills.
I have also written a compiler and my own language as well as an operating system, and its usefulness has come up exactly once in near 15 years in the industry, and that was a very niche topic. Explain why, exactly, you need to know compilers and operating systems to write any modern day app.
Also, I don't have a CS degree and that's not what I advocate for. I advocate for developers who spend years honing their skills and learning fundamentals of the craft.