You're not wrong. And this isn't bulletproof. But small n studies are often needed on a particular subject in it's academic infancy almost like a proof of concept. A meta analysis like this helps expand or elucidate things that small n studies can't. They can all then be used to pitch for funding for the larger, more representative, more comprehensive studies.

In that framework, I see it as still very useful science, even if it's not entirely settled.

I only skimmed it myself. But it's a meta-analysis of 34 other published studies, so the sampling methods would be found in each of those respective studies.

I was just confused as to why there was criticisms of the sample size (almost 3000 is usually considered decently representative so long as it's properly randomised as you highlight) and the methods (which specifically included gaze tracking). Not here to argue over anything other than those specific criticisms, both of which are answered in the first few paragraphs of the article.

N≈3000 meta analysis, including gaze tracking that you require, isn't reliable?

Genuinely not trying to be a prick, but did you read the link? I'm not sure what your problem with it is...