There's probably something bottlenecking the hardware on the older systems that's preventing 720/60 on older hardware. Or, the base consoles might target 1080/30, but have something in place to keep performance up, like a dynamic resolution. Or, the game drops below 30FPS on the regular. Who knows for sure?
What if I told you that 720p was the most common gaming resolution for PC gamers according to Steam stats with 900p being second. Both of those resolutions combined make up the vast majority of current Steam users gaming resolution.
Less than 15% play at 1440p and less than 5% play at 4k.
If it’s a rock solid 60fps and 1080p with good anti-aliasing and effects I’m okay with it. I’m still debating on whether to go for the Xbox One X version or the PC version. Uncapped frame rates on the latter is a nice incentive.
I've come around on mostly wanting 60 fps over higher res when it comes to shooters at least. Now for something drenched in atmosphere like Metro Exodus I absolutely appreciate 4k, but something like Rage 2 as kinetic and frenzied the shooting appears to be it feels like something you want to be as fluid feeling as possible.
If you own a 4K display, it's kinda annoying to be limited to 1080p res anymore. Even most console games aren't sharp (jaggie, low AF, use bad visual effects to hide them) enough on 1080p displays, let alone 4K ones...