8K is largely pointless as a broadcast format and marginal even as a digital cinema format. 4k is already at the outer limits of visual acuity. Someone with 20/20 vision can only resolve about 60 pixels per degree, so you need to be sitting six feet away from a 50" screen to even notice the difference between 1080p and 4k. Unless you're filling your entire visual field with pixels, 8k offers no appreciable benefit.
What does matter a great deal is HDR and 10-bit colour. Human eyes can perceive about 20 stops of dynamic range, but the best cameras max out at about 15 stops and most TVs struggle to exceed 8 stops. A typical TV only covers about 40% of the visible colour gamut, with particularly pronounced deficiencies in green and cyan.
The benefits of HDR are slightly harder to explain than "more pixels are better", but the difference is visible at first glance.
You must have exceptionally good eyesight. For someone with 20/20 vision, 5k is the limit of resolvability for a 90 degree angle of view. A typical cinema configuration gives an angle of view of between 45 and 60 degrees in most seats.
Going beyond 4k in digital cinema projection will have some benefits, but they won't be perceivable by the majority of people in the majority of seats. In the extreme case, someone with perfect eyesight sat on the front row can see up to about 11k.
A far bigger issue is the deprofessionalisation of projection. The overwhelming majority of cinemas no longer have a fully trained projectionist. As a result, serious errors in projection are commonplace. There's a huge amount that can go wrong between the DCP and the screen; without a trained person in the projection booth, it's left to the patrons to notice if a film is being projected out of focus, in the wrong aspect ratio or at the wrong brightness.
What does matter a great deal is HDR and 10-bit colour. Human eyes can perceive about 20 stops of dynamic range, but the best cameras max out at about 15 stops and most TVs struggle to exceed 8 stops. A typical TV only covers about 40% of the visible colour gamut, with particularly pronounced deficiencies in green and cyan.
The benefits of HDR are slightly harder to explain than "more pixels are better", but the difference is visible at first glance.