What's wrong with low contrast?
Some say that grey text looks closer to print. However print doesn't have a backlight or shiny glare,
Trying to make light emitted from an array of IPS LEDs abstractly mock dyed paper to increase legibility is a complete joke. The abstraction is wrong.
There are a wide variety of displays these days used in a wide variety of lighting conditions.
Take any two random devices and put your grey-on-grey text website up against it. See how the greys are strikingly different? One of them is bluer, or greener, or lighter, or darker. Notice how the contrast ratio between the black and white are different?
Want to increase your convergence? Lower your bounce rate? Get those engagement numbers up? Legibility is important!
Sub-pixel font aliasing engines differ for each browser and platform. Things that look good in one combination may look terrible in all others. This goes back to the most basic fundamental rule of making webpages:
Test your stuff in other browsers on other devices.
People have varying degrees of dyslexia which mean that reading for some requires much greater concentration than reading for others.
The problem is that if a bunch of concentration is exhausted to interpret the hairline grey flicks you call letters, then there's not much left to be spent on trying to understand what you've written with it.
A/B test it. I have. Higher contrast = better performance. CTA buttons, headlines, pitches, everything performs better with higher WCAG contrast - every time. I can incrase your sales by double or triple digits with two words: Increase Constrast. Really.
So we have the following realities:
You should fall back to the highest contrast possible - leaving the most room to accomodate for this differences. Make sure:
You will have more users better able to focus on your message without being distracted by your medium.