Everyone's monitor is calibrated differently. That can massively affect readability on low-contrast text. Plus, those letters are a little blurry there, too, which doesn't help.

I can read it on my monitor calibrated with a calibration device, but it's not comfortable.

Unless you have vision problems you don't know about

Yes exactly. The contrast of text should be enough so that it doesn't matter much.

White, regular styled text on grey is destined to have a low contrast, so by design it is not "very easy" to read.