As I said, visually a $3000 OLED and $6000 OLED are pretty close to the human eye without instruments measuring numbers and the same goes for this year's $3000 OLED and 2 year's ago's $3000 OLED. The difference come from other things like size, audio quality, image processing, features and services etc. I was just discussing the Panel and not the TV as a whole, sorry if that was not clear.
The samsung 7 series is the lowest and cheapest TV samsung sells over 43 inches from what I could find. There is a 8 series (mid range) above it and a 9 series (high end) above that. Input latency doesn't really determine low vs mid vs high - as the cheapest panel could have the lowest latency and sometimes is. To get a really low input latency on a TV requires switching off as much image processing as possible and since the 7 series is going to have fewer image processing features to begin with, it's no surprise that it has a lower input latency than the 8 series, 9 series and other mid range TVs.
What makes the 7 series an entry level Samsung TV is it's 280nit HDR brightness (most mid range panels get brighter), Edge Lit panel with no local dimming at all (most mid range TV's have at least some dimming zones), an image that degrades at an angle, 8 bit panel instead of 10 bit (most mid range TV's use 10 bit panels), Only having 3 HDMI ports (most mid range TV's have 4 or more), lack of gaming features the 8 and 9 series has, lower quality anti reflective coating than the 8 and 9 series and worse motion handling (posting a pixel response time of 20ms!) than the 8 and 9 series so fast moving objects have more blur behind them