Is this really some unsolvable problem? Seems like a cool opportunity for UX innovation. That shimmer looks kinda like a moire effect to me, and probably isn't an issue at higher zoom levels? I wonder if there an opportunity here to explore other ways of navigating a spreadsheet, like maybe panning and zooming the UI like a map, almost. The longer you stare at an area, the more it zooms in so you can easily see just a few cells at a time. You can still have a minimap nearby to see the big overview, but your main focus would be on just a few cells.