Seven or eight years ago I watched the 2012 Jaws Bluray, which of course represented an HD upgrade. It was entirely pleasing — robust color, ultra-detailed, excellent sound.
How much better can the 4K be? If you’re watching it on a 65-inch 4K HDR screen, which is what I own, the difference between the 1080p Bluray and 4K HDR is not really that huge. The colors will probably be stronger, but that’s all.