I dunno, I recall hearing (and believing) a similar thing about the iPhone 4 retina display. Seen an iPhone 4 display recently? It looks fuzzy by modern standards.
Point I’m making is there is more than just DPI making those new panels look much better. The panel on the XR is the same DPI as the 4 and is widely regarded as one of the best, most colour accurate LCD displays Apple has ever shipped.
The vast majority will not notice the difference between 2x and 3x retina, to borrow apples technical terms for the different densities - beyond a certain point display DPI is a pure bullshit vanity metric for a given size/viewing distance.
For me personally, improvements in screen lamination are some of the biggest differences - on modern iPhones the screen feels directly laminated to the glass - on an old iPhone 4 there is a very noticeable “air gap” between the display and the glass.
And about every mid to hi-range Android phone that came out in the past 5 years.
I haven't seen the Xr yet but the lower resolution is extremely obvious on the non plus iPhones.