I’m a mid-level backend dev, ~3 years YOE. I wanted to seriously start thinking about expanding my skillset and learning new stuff / new technologies outside of my daily tasks. But I’m unsure of how to start, how to decide, what would be most helpful to my career, etc. Any advice?
This is solid advice. Learn the fundamentals, and maintain conversational knowledge of more cutting edge tech. As you get stronger in the fundamentals you’ll be able to speak intelligently about why you might choose to use some new fangled thing.