The learning curve of Magento can be pretty high, especially if you are new to the framework. In general you can take online courses to learn the basics, read the docs for clarification and follow other developers to stay abreast of practices used.
The fundamentals should only take a week or two to get down; and really, there is nothing earth shattering about how Magento is developed or what patterns it's using. Truly understanding how each element comes together to build a page or fulfill a request is going to take time and attention. There is no better teacher than experience.
If you want high quality reusable code that requires minimal maintenance between versions of Magento, you will invest the time to really learn where files go, how to properly add features and use plugins to modify existing functionality. If you just want to throw something together and not care about how well it functions, you can still develop a simple module in a day.
So in practice, for me at least, to be a Magento developer is to be active in the community, follow well known developers and businesses, read the documentation often, attend the online trainings, take extra time to really think critically about how your module will work and interact with the core, and follow all the guidelines as laid out by the Magento core team.