[kazinator]

Some books on compilers go into the automata theory for the following reason: they teach about the workings of tools that generate lexical analyzers and parsers. A compiler writer is usually just a consumer of those tools. The skills that come into play is being good in program design: structuring code and data.

How much CS comes into play depends on how advanced you make the compiler and what design choices you make. E.g. if you make a stack-based VM, or one with unlimited registers, instead of targeting a real machine with a fixed number of registers, you don't have to study the algorithms for register allocation.

Some languages avoid the complexities of parsing, such as those in the Forth family, and to a large extent Lisp family. To make a language, you don't even need to be a consumer of scanner and parser generating tools, let alone understand how they work.