I see this often with both new and old developers, they have one way of doing a thing and when presented with a new problem they will fall back to what they are used to even if it's not the optimal solution. It will probably work if you bruteforce it into your usual patterns but sometimes, a different approach is much easier to implement and maintain as long as you are willing to learn it, and more importantly - know it exists in the first place.
On a less abstract level, I guess my question is - how would I go around learning about different design patterns and approaches to problem solving if I don't know about their existence in the first place? Is it just a matter of proactive learning and I should know all of them in advance, as well as their uses?
Let's for example say I need to create a system for inserting a large amount of data from files into the db, or you need to create some service with many scheduled tasks, or an user authentication system. Before you sit down and start developing those the way you usually do, what kind of steps could you take to learn a potentially better way of doing it?
I guess the most important advice about learning that I always try to pass on is: Do NOT go passive. Reading books, watching videos, etc. is all fine, as long as you question everything about what you have read or seen. This is something I see especially with juniors but also quite often with seniors. They get recommended a book, and because the author has a name in the industry or simply because its written in a book, it must be Gods holy truth and everything must be done exactly as decreed. In out industry, knowledge has little value without application, so unless you can put the things you consume into a context that makes sense for you foremost, for your team and for your project. If you struggle with this (not everything can be time boxed into a lazy Saturday afternoons) try to discuss with your peers and form some context that way. Do not just consume, you will not improve that way.