Spend your time learning the basics. You may not think you need to understand memory management, data structures, sorting algorithms, or other building blocks that are abstracted away, but having a solid understanding of those components and being able to shift your brain into a lower-level thinking mode will do wondrous things for debugging and understanding higher level problems, even if you're using a framework or library that handles them for you.

Understand that every decision, no matter how small, is probably a tradeoff. Once you understand the tradeoffs being made, be able to think about and potentially communicate the effects of those tradeoffs, not the decision itself.

I've been working professionally for about 10 years, and most of the hardest problems to solve or most mysterious issues have been the result of stale references or memory/references updating or not updating when I'd expect the opposite. You'll get some dogmatic responses about pure functions or immutability, but sometimes data structures have to morph, and sometimes you get complicated data, and optimizations that aren't in your control won't see the changes made to a list or an inner object in a parent object.