218 PPI seems awfully specific. The current 14” and 16” MacBook Pros are 254 PPI for example.macOS has been designed to have the best experience using a display with a pixel density of 218 PPI. It does not matter if your display is 4K or 5K, if the display is not 218 PPI than your Mac will have to use "scaling" and the further from 218 PPI your monitor, the worse the "scaling" will look (i.e. blurry pixels). Now, "worse", can be highly subjective, but once you go "Retina" (218 PPI, 60Hz), you never go back ;-)
The thread is in the context of external displays. All 4K and 5K iMacs are/were 218 PPI specifically. The Studio Display and XDR Display are 218 PPI specifically.218 PPI seems awfully specific. The current 14” and 16” MacBook Pros are 254 PPI for example
Hence “worse” is subjective.I use a 24” 4K display at about 185 PPI and it looks fine to me.
When it comes to scaling on a Mac, there are several issues to be aware of -- such as blurriness, moiré in patterns, and shimmering when scrolling. The following article details some things to be aware of.
Mac external displays for designers and developers, part 2 (bjango.com)