This is especially true with HiDPI screens. If your primary content is textual in nature, then using low contrast colors is disrespectful to your readers. This

This is especially true with HiDPI screens. If your primary content is textual in nature, then using low contrast colors is disrespectful to your readers. This is amplified when designers don't use relative scaling units for font sizes. Medium.com is a good example of presenting readable content, independent of DPI. But many sites require substantial zooming to read comfortably, even with perfect vision. Another major usability issue is disabling pinch-to-zoom on mobile devices. This is a behavior that users have come to expect. I've had to explain to several older people that their iPad isn't broken when they couldn't zoom in on a product while shopping.