to what extent is white text on medium-to-light grey background objectively bad practice?

I made the mistake of openly criticizing a webpage because I was asked to have an opinion. I ruled negatively. To what extent is the designer culpable for my unfavorable critique?

Legibility judged objectively?

Intrinsic and external factors like monitors and eyes play a role here.

Small, 8 to 10px, white sans text, on a solid shade of gray, that is somewhere between 10-35% still caused me to drop a "star"... probably because the lcd screen helped. Screen viewing angle, pixel density, maybe even screen reflection might have influenced me. Yet am I to blame or is this supposed to be avoided ?

Given that I have slight astigmatism, I shouldn't appreciate tiny fonts that are too thin or light at all. But I actually use this very setup right now for my desktop environment, with supbixel rendering enabled being a necessity to render the font properly, it's so thin. I'm not blind.

Is it tenable that one shouldn't be needing to weigh such external factors, if one sticks to good practices, like higher contrast between text and background ?

There was also no real necessity on picking such a light grey. Which in end effect gave me the impression of carelessness - while the author might have tried to keep things warm and cozy with his choice of colors.

Relevance issues

The thing is, the user isn't reading a poem with this setup. I'm talking about menu items that are only going to be actually read until the user learns instinctively click on the 3rd word in the row.

I personally believe legibility is important. But good practices aren't rules and I can't penalize the author because he trespassed against Article X. Is this still somehow objectively a faux-pas from an UX perspective or is it rather that I was prone to simply subjectively "finding fault", frustrated that I couldn't read a few words on a glance ? To what extent is white text on light grey background objectively bad practice?

Bonus question along the same lines:

This menu was also unnecessarily hiding from view, until being called upon through a click. This superfluousness made me drop another star, as it gets in the way of efficient interaction. Except, it's only one extra click. Sneaking in dynamics for the sake of having dynamics can be done without it getting in the way though.

Same question. Did I hold a valid grudge ? Should the author get it or rather get offended ?