What you're describing is only the most basic idea of what a Skybreaker is meant to be. It's like saying its easy for a Windrunner to uphold their ideals because all they've gotta do is use their powers to protect people.

As a Skybreaker progresses through the ideals, they're supposed to really think about what justice means, and how it can be properly executed. At the start of the journey, there's a focus on law because it's an external code to remove personal biases and focus on objective justice, but it's an immature ideal. As the Skybreaker moves forward, they have to really think about what is or isn't just, and choose a more personal and specific code, and then use that to guide their decisions until they can find a better ideal. This is basically what Szeth's second ideal is all about.

Szeth in particular speed runs the Skybreaker ideals because he's pretty much already a perfect Skybreaker. He knows how to put a code before his own subjective feelings, but has also seen the harm that can come when he follows the wrong people, and can start determining justice for himself.