This depiction of the Peer Reviewer Selection Process shows just why site-reviews have been characterized as incestuous.

This Peer Reviewer recruitment process constitutes a closed system, insulated from the outside world, as it is intended to be. Reviewers are proposed from one institution for reviews at another – a kind of self-review.

But also notice that the reviewers are also drawn from the social networks of the Commission itself, which is just another way of saying that they are drawn from the institutions themselves (again!). This incestuous pattern of recruiting does not have sufficient internal controls against potential conflicts of interest, and is blatantly self-serving.