I think it's a complicated topic.
IMO, there are two key criteria for monitors. Real estate and pixel density, and in some cases, you can't get both affordably.
I have had 15" laptops with 4K displays for some time now. I love the pixel density. But I can't do certain types of tasks on them because I end up getting real estate anxiety. I feel so constricted on a laptop screen, even when I add a second monitor.
My desktop has 2 x 27" 4K monitors running without scaling. So I have plenty of real estate, but the text could look nicer. Having said that, I don't miss sharp text in the same way that I miss real estate when using my laptops, at least from a productivity perspective.
I don't think a 5K screen is an answer for me, because my first urge would be to try to use it without scaling for more real estate.
On the other hand, a pair of 27" 8K screens (does such a beast even exist, and is it affordable?) would be ideal, because 1:1 scaling on such a beast is impossible at that monitor size, but 200% scaling would basically give me the same workspace real estate that I have now but with super sharp text.