You should try doing a game jam (or, multiple!) You have an extremely short time frame, and each time you start from scratch so you learn what systems work and what doesn't in a practical way that doesn't allow for perfectionism.
I've probably implemented platformers physics about 15 times now, and have a pretty good idea of how I personally like structuring game code.
I do game jams and you’re right about their benefits.
I’ve done them using TDD as an inexperienced game dev, test free, TDD now that I have more experience, and it’s helped me clarify some of my own thoughts on how automated testing can fit into my workflow.
I've probably implemented platformers physics about 15 times now, and have a pretty good idea of how I personally like structuring game code.