Don't waste time trying to learn and develop style. Don't waste time studying other code just for the sake of learning how to write better code. Don't waste time reading generic things on how to write better code.
Put the effort in to learning new concepts, programming languages, methodologies, programming language history, computer science, and even broader subjects dealing with humans and how we think and form ideas. There are countless ways to write code and without having a broad knowledge of them you will only at best reach a local optimum and rarely choose the most effective solutions and designs. The worst thing you can do is stop learning and seeing other perspectives.
* Software development methodologies, things like Mythical Man Month
* Computer Science history and basic theories and concepts
* Compiler implementation techniques.
* Anthropology and related subjects. Programs are written by people and for people so understanding people helps a lot.
The biggest thing is to approach things from all perspectives and an open mind. Learning programming languages of different types is great because the different language families highlight different techniques, concepts, and ways of thinking. No one approach or language is the perfect solution to everything. Try to aim for the largest perspective: functional, homioconic, machine like, pure OO, strict, lose, etc. You can look at the lineage of programming languages and what developed and derived from what and learn one from each group to get the broadest perspective.
Learning CS history and basic theories might not be directly applicable to your life but the knowledge that comes from it will show up in everything you do and knowing how to leverage it makes a big difference.
The value in learning about compilers, GCs, etc comes from being forced to learn, in depth, languages themselves and concepts behind them. If there was anything you didn't learn in depth in other areas they will probably show up here.
Everything you learn about programming and CS is ultimately dependent on humans and how we interact with computers. Understanding how we think will help you develop long lasting programs that are easier to understand and use.
Depending on your goals it may be useful to learn about the basics of how the hardware works, although that is more related to performance optimization than good design and good code.
Edit:
Learning about so much is a long process and never ends but if you want to write solid code long term, and not just do what's popular at the time, it's the best way to go. Just take it slow and do it at whatever pace works. It works best if you have toy (and not toy) programs to make in each language as you go. After you've started getting a broader perspective, in things like programming languages, it all becomes a lot easier and faster. You'll be able to learn completely new languages in a matter of days and be better at them than people that have been doing it for years, because you can break it down in to its fundamental concepts and all you have to do is learn the language libraries and syntax, which also starts coming quickly after awhile.
I think I take a lot of the above for granted. It all sounds like a solid CS education to me, something which many students already have.
So I think your point about being open minded is the strongest. Additionally, you bring up some excellent summaries of what each discipline is about. A lot of the time the failure here is lack of comprehensiveness, or coverage; coverage in space (what's out there) and coverage in time (what's been done historically). Current favorite example is APL: http://isomorphism.es/post/146379365169/unlike-many-language...
Most metaphysics is crap, but there are a few gems. Whitehead, Russell, Quentin Meillassoux, Wittgenstein, Northrop, Peirce, Kripke. Dealing with fundamental conceptions of space, material, time, cause, and uncertainty can go a long way when it comes to modeling code and understanding when it will correspond to reality. Programming languages give you enough flexibility to reach your ass and fuck yourself over. That needs to be constrained.
tl;dr
We're in agreement, I just like hearing myself talk.
Put the effort in to learning new concepts, programming languages, methodologies, programming language history, computer science, and even broader subjects dealing with humans and how we think and form ideas. There are countless ways to write code and without having a broad knowledge of them you will only at best reach a local optimum and rarely choose the most effective solutions and designs. The worst thing you can do is stop learning and seeing other perspectives.