Boring, perhaps. But definitely not harder to read. The old styles with text against textured backgrounds (for example, the pinstriped menu bars) detracted from readability. Current design is significantly better, especially dark mode, although lately there is a trend towards low-contrast UI (text against similarly-coloured backgrounds) in recent versions of iOS and macOS which is also detracting from readability, IMO.
The pinstripes were only in the earliest versions. By Leopard/Snow Leopard (which i also find the best one) the theme looked clean without looking flat.
pinstripes, brushed metal, linen; one could follow the trends by looking at cargo-culting designers were setting as the background image on their blogs. I'm sure they thought it looked good when viewing on their freshly updated Macs.
