In reply to Giorgos Sarigiannidis.

– Not all ratings are equally useful. For example, giving WP-Rest API one star because “I didn’t understand how to use it” is misleading about the plugin’s actual value. Perhaps a button “I found this review helpful” under each review would make sense on that direction.

Rating reviewers could be useful in that case.

Of course, that leaves it open for flamers, petty revenge and jerks who want to undercut someone who didn't leave them a glowing review.

Instead, they could use the data from the existing WP.org profiles. "Member since..., plugin developer, etc." would give some idea of which reviews have more merit. A newbie review would carry less weight that way.