Actually, no. The paper may not have been explicitly clear about this, but the ENTIRE point of a "data visualization" system is to transform potentially high-dimensional datasets, with a large number of columns, into meaningful images by a series of steps. You seem to be interpreting this narrowly, and imagining that geometry is already pre-defined in the dataset, so then of course this looks like a fairly trivial 2D accumulator.
That is not the intent, nor is the common use case.
For data visualization, the question of "how do I accurately aggregate or accumulate the 25 - 1million points in this bucket" is a deep one. There is NO data visualization system that programmatically gives access to this step of the viz pipeline to a data scientist or statistician. Most "infoviz" tools gloss over this problem - they do simple Z buffering, or cheesy automatic histograms of color/intensity, etc. These are almost always "wrong" and produce unintended hallucinators.
Your first comment - about "not needing all the geometry present" - indicates that you are not understanding the nature of the problem datashader was designed to solve. There is no simple "cull" function for data science; there is no simple "Z" axis on which to sort, smush, blend, etc. At best, your data points can be projected into some kind of Euclidean space on which you can implement a fast spatial subdivision or parallel aggregation algorithm. But once that's done, you're still left holding millions of partitions of billions of points or primitives, each with dozens of attributes.... what then?