But I genuinely believe 4k is the upper limit where you stop seeing benefits in increased resolution for a monitor. Our eyes do have limits after all! I have pretty good vision and 4k is enough, and at that point I'd prefer focus on other aspects of picture quality like color accuracy and higher refresh rate.
It's already annoying enough how large a screenshot of your monitor comes out (just tested on my desktop and it came out to 10MB). 8k is unnecessary in the vast majority of cases.