Pretty weird that you would claim to know what someone else can and can’t perceive.
For about 18 months I used dual 27 4K in the office and dual 27 5K at home, same seating distance, and I could tell the difference in sharpness and density.
That said, I agree that 27 4K is typically adequate for most people for a “retina-like” experience.
To be fair, the math says it is highly unlikely the difference you saw was due to the resolution itself. You have to be within 21" of a 27" 4k monitor to be able to distinguish individual pixels. Obviously there is variation from person to person, but at a normal desk setup, the monitor is usually going to be at least 24" away from you and often something more like 27" or 28". More likely what you are seeing is either better calibration or different settings (particularly with brightness) along with macOS's inability to do non-integer scaling well. All of those things could be fixed in a 4k monitor if Apple wanted to. Instead, they want to be one more than 4k for marketing reasons.
A few days ago, people were predicting the new display would cost at least $2000, probably $2500 or more.
So, Apple introduced a display for $1600, and everyone’s all “insane prices, yadda, yadad….”
Since everyone else is complaining about the Studio Display, let me be the first to say I’m disappointed in the lack of a notch.![]()
I think people were assuming specs that would be handily beat 5 year old monitors. That didn't happen.