Why does the new 720 P not feel like the old 720 P?

Back in the 2000s, 720p was considered HD, and most of our downloaded movies were in that resolution. But if we go back and check the same files now, you'll notice pixelation that wasn’t apparent before. Why is this happening?

    Well, at that time, our monitors and screens weren’t HD; a 1080p resolution, the basic HD standard, was considered impressive back then. The pixel density of those monitors was much lower compared to today's screens. Now, we have 2K and 4K resolution displays on our smartphones, where the pixels are densely packed. Playing 720p content on a 4K monitor feels similar to watching 3GP videos on a 1080p monitor.

    So technically, 720p hasn’t changed; it’s just that we've upgraded our devices to the point where 720p now appears to us as a pixelated, low-quality image.