I have both a 15" MacBook Pro (2018 model) and a Lenovo Thinkpad Carbon X1 open in front of me right now. I have 20/20 vision and it really is not striking me as that much better. I spend quite a bit of my day in a terminal and the remainder looking at the web, so font rendering definitely matters. Even with Linux's abysmal font-rendering, the mac really doesn't feel like it has the edge.
Wait, what? It's somewhere in the middle between Windows (too pixel-fitted) and macOS (too blurry). FreeType, slight hinting, LCD filtering on is the best font rendering that I know.
20/20 vision is only average for the population when you get to 60. So most people here will see significantly better than that. At 20/20 1080p is probably enough. Most people will enjoy a 1440p screen and 2160p will have marginal gains but it may be helpful to be able to use 2x scaling instead of needing fractional steps. But that depends on how you drive it.
Font rendering was matter on Low-DPI monitors but IMO not much matter for HiDPI monitors because some techniques like anti-aliasing is no more needed. Fonts are still important.
Hmmm, as an engineer, I have my vision checked every year. While a difference is discernible, it's not enough that I'd "miss it" if I didn't have a retina display. (I just ordered a Dell XPS 15 this weekend, I purposely left if at FHD as I didn't see the need for 4K on a laptop)
