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.
This is really difficult to overcome without some kind of structure. I was really enthusiastic about infinite canvases, but I lost interest when I realized that screen readers would not do well
1. Ambiguous structure - users cannot easily glean the structure of content from the layout alone. For instance, on an arbitrary canvas, you don’t know if two things are close to each other to indicate a relation, or just for aesthetic reasons. This can be mitigated by ensuring relations are exposed in other ways, but unless everyone is super strict about including an underlying structure, this will always be an issue. Also, without a representation of the underlying structure, an infinite canvas is fundamentally inaccessible.
2. Navigation - finding all possible content on a canvas is hard. This can be mitigated with something like a mini-map, but frankly sticking to one dimension of “infiniteness”, eg scrolling, has shown to be the most effective for the average person to handle.
3. Implicit, but heterogeneous, affordances - when you have an infinite canvas, there are many more actions needed eg. pan, scroll, select, possibly lasso, possibly zoom…all of which need a mouse movement or keybinding or touch gesture, depending on the device and context. These all need to be discovered, or taught, and are often initially hidden from the view. This makes the learning curve far steeper, especially when users are accessing content from many different types of devices.
4. Responsiveness - it’s hard enough to make a paragraph of text easily viewed on multiple screen sizes, let alone a complex layout of objects with relations possibly conveyed spatially. Infinite canvases are difficult to reformat to get a good, legible layout on a screen other than the one the creator used. There are workarounds, but they often lose information unintentionally by repositioning items in ways the author didn't anticipate.