You can see in the graphs above that even thought the 6800XT is ahead in 4k. It's not hitting 120FPS on all games.For most people, I think so,
Getting 120+fps in 4K with good graphics setting requires some pretty expensive hardware, however you can run 120fps in 1440p with ultra settings for a far more modest budget, and it's a big leap in both resolution and graphics from previous gen consoles.
6900XT or 3090 will be required for 4k gaming. £1000-1500... as you say 1440p is much more achievable on a budget.