None of what you mentioned is theory expect for Mathematics, probability, formal methods and algorithms.
Stuff like design patterns, system architectures and software strategies are like flavor of the week stuff. Opinions basically. Patterns like microservices are bad or good depending on opinion, but theory is always correct.
Theory gets less bang for the buck but it's always what many programmers especially self taught ones are missing.
Theory is so hard that it will be hard to see applicability until you're a more seasoned programmer. Many seasoned programmers get by without ever knowing theory. But you will be a better programmer if you know it.
If I were to recommend one theory to study it would be category theory. If there was any true axiomatic theory for design patterns or how to design programs... categories are it. The study of morphisms is the study of the simplest form of a compose-able module. Knowing this theory you will begin to understand why Some design patterns don't work and why it's sometimes hard to reuse patterns in code that was that not properly designed. Theory doesn't answer all questions but for the questions it does answer you will get a definitive answer and not an opinionated one.
Stuff like design patterns, system architectures and software strategies are like flavor of the week stuff. Opinions basically. Patterns like microservices are bad or good depending on opinion, but theory is always correct. Theory gets less bang for the buck but it's always what many programmers especially self taught ones are missing.
Theory is so hard that it will be hard to see applicability until you're a more seasoned programmer. Many seasoned programmers get by without ever knowing theory. But you will be a better programmer if you know it.
If I were to recommend one theory to study it would be category theory. If there was any true axiomatic theory for design patterns or how to design programs... categories are it. The study of morphisms is the study of the simplest form of a compose-able module. Knowing this theory you will begin to understand why Some design patterns don't work and why it's sometimes hard to reuse patterns in code that was that not properly designed. Theory doesn't answer all questions but for the questions it does answer you will get a definitive answer and not an opinionated one.