Let's review the constitutional authority for the census, from Article I, Section 2:
Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers .... The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct.
The purpose of the census is to determine how many US Representatives each state gets and how much of certain taxes each state pays based on population.
The method of the census is to count how many people there are. Not their races. Not their religions. Not their sexual orientations. Not their incomes. Not how many toilets they have in their houses. Just how many people there are. That's it and that's all.
Of course, the census form includes a bunch of verbiage intended to convince you that you are legally obligated to answer all of the Census Bureau's other nosy questions.
So, in 2010, I did answer all of the Census Bureau's other nosy questions. I answered the constitutionally authorized question, regarding how many people lived at my address, with the correct number. As for the others, my written answer to each one was "none of your business."
I don't recall that I ever heard anything more from them, so I guess that was good enough. And it will have to be good enough in 2020 as well.