In the 90's/2000's, typical screen size also grew from 15" to 20"+, so the DPI didn't really change a lot, did it? The text size in OS X has never been adjustable, and in Windows 95+ you could only tweak it from 100% to 150% or so, which would still look good next to text that had a fixed size.

This time, the screen size stays the same, but the DPI goes through the roof.