> If you're building a JSON object, you can just not write the code to format some fields out.

Did you fail to read the article somehow?

Few if any modern language requires you to write the code to format individual fields out. Even Go does not, though when it comes to json most fields need to be annotated because of the choices it made to tie casing and visibility, but then it doesn't even require you to opt the type itself into being serializable, every struct is serializable by default.

Skipping fields on a serializable structure is what requires extra work.