It is the Constitutional responsibility of the Census Bureau to count. That does NOT mean build a website then mail a letter and a postcard, or otherwise advertise the census. Beyond this delegation of their responsibility to the populace, is the extraordinary gall of assuming that everyone in the United States is on the Internet. So, sorry, that means actually going out and counting people.
That could take a while. It will cost a lot. That’s OK. We have a large country.
It seems, as a casual observer, as if someone were trying to pinch pennies and reduce labor costs, by only physically going to those addresses on record for which no form was returned, even before COVID-19. It also seems, again only as a casual observer, as if an arbitrary internal deadline for completion, such as the first Monday in October, is a useful means of avoiding counting everyone.
This is often the problem with measuring things. Sometimes the numbers aren’t the ones we want.