My take is that many a time, family members close to the couple often make a bigger mess than it initially is, mainly because they often end up making it a fault finding mission. More often than not it becomes 'she is at fault/he is at fault' rather than seeing the root cause of the problem. Also, often, the individuals involved might not take the advise given by their family members seriously labeling it biased if they are labeled the wrong party or made to be the source of the problem.
In India at least, the onus to make a relationship work lies almost 90% on the girl, so chances of getting a fair judgment would be remote, as the in laws often blame their daughter in laws and the parents don't want the burden of a separated daughter. On the other hand, sometimes parents who have too soft on their daughter or cannot see beyond her can give out unfair advise as well. So fair enough to say the hearing by the elders in most cases could turn out to be partial.
Any couple that I know, would have their respective parents dissing out at the opposite party or end up pressurising them to stay together. Actually making them understand and see reason which will make the marriage work in the long run might not happen at all.
I believe marriage councilors could be a better option. I have seen that work in many instances. Maybe because when the involved couple shells out money, the advise starts making more sense than the elder family members who do it free and then get labeled biased, which unfortunately many cases they are.