Census data is relatively easy to get used to once you know how the geo formats work and you are willing to work with their geographies. They have a nice API to work with (api.census.gov) and I think that it is going from its current array of arrays format to full JSON later this year.
That said, the app does two cool things that I have not seen anywhere else:
(1) Arbitrary geographies, like drawing a circle or a polygon of your own choice, requires significant additional work. The app mostly does this with procedural SQL and PostGIS on the back-end.
(2) Longitudinal reporting. The Census bureau changes the geographies every 10 years to some degree, so geography with id "foo" might not be the same area in 2010 as it will be in 2020. This is solved by "virtualizing" the geography and is relevant to the same concepts for handling arbitrary geographies.
Happy to chat more if you have questions!