Higher pixel density can help a bit if your vision is bad enough that you use a lot of screen magnification, as it means that the magnified text will be better-

Higher pixel density can help a bit if your vision is bad enough that you use a lot of screen magnification, as it means that the magnified text will be better-rounded and fuller, rather than almost unrecognizably pixelated. For some visual impairments, though, the improved sharpness from higher DPI may be basically undetectable, which sounds like what you're reporting.