Counterpoint: spreadsheets are Infinite Canvases, and are quite successful ...
The trick is getting the amount of structure just right, not too much to be too restrictive and not so little that users are lost in the way the person you're replying to describes.
Excel handles this better because navigating around a large sheet feels more like "snapping" as there's no UI motion as your view zooms in and out. Plus with shortcuts like CTRL + rArrow, which immediately snaps your selected cell to the rightmost end of the current range of cells, the infinite canvas feels downright zippy. Excel sheets also have tabs that signal to the users about how they can split up their data instead of filling up Sheet1 with every scenario. Infinite canvases make you create a new file.