QuickDraw's model allowed for it to be scaled for printing
You think you cannot scale up DirectX?
and it had standard scalable fonts.
QuickDraw and Color QuickDraw both predate Mac OS support for scalable fonts, which did not occur until TrueType. Previously you had to use Adobe Type Manager software to get scalable fonts, and all pre-TypeType fonts provided by Apple were bitmaps. That's why 1) fonts came in sizes, you had to add all of the sizes you wanted with the Font/FA Mover and 2) when you scaled system fonts up for printing, they looked like shit, as demonstrated by printing them on a dot matrix printer like an AppleWriter. Scalable fonts were embedded in the LaserWriter and other Laser printers, which at the time would sometimes come with bitmap screen fonts for your Apple, which again didn't support scalable fonts AT ALL out of the box.
The drawing commands were saved in a data format called PICT which was a no-code version of the drawing commands which also could include pixelmaps
PICT format was limited to primitives and bitmaps and "QuickDraw" performance was trash unless you had a 8*32 GC (not just 8*32) NuBus card, until the Quadra line. No other prior Macintosh models had graphics acceleration. Leave it to Apple to produce a graphics-only computer with no graphics acceleration hardware.
The psychologists and the designers of the past did better UI
They were creating UI with a tiny percentage of the features of modern UI which ran on a computer with less power than the baseband processor in your cellphone. They had a lot less work to do.