There are various aspects to the 4k format. There is the increased resolution, wider dynamic range ( HDR vs SDR), wider color gamut. When they are talking about "appreciating the 4k upgrade" they are usually referring to increased image resolution, which is a function of visual acuity, distance from the screen, screen size. They are mostly correct in that regard if you are comparing images with SDR and the same color mapping/gamut. Besides a good portion of the 4k material is actually upsampled from a 2K (HD) digital intermediate. However typically most 4k material these days includes HDR and WCG which are easily noticeable , you almost have to be blind to not notice.
I finally broke down and bought a 55" LG C8 OLED TV last week after lusting over it for the past year and a half. I just couldn't justify getting another TV while it was still working. Hopefully it will be delivered this Thursday.
I may hit you up for some tips on settings and calibration for the TV.