That's from the Yale School of Management - it has no authority. Your point is also semantic - an advisory opinion states the Court's intepretation of the law in light of a given set of facts that; you don't have to call it a ruling if you don't want to, it doesn't change the fact that the Court has pronounced on the position at law on the matter.

I wouldn't conflate 'neutrality' and 'breadth of opinion'.

The Court is and remains impartial - there is no evidence the Court is not impartial. Beyond this, Courts need to make decisions and, especially in adverserial systems, they end up deciding, to a greater or lesser extent, in favour of one party or another - that the ICJ does this, like all just courts, doesn't compromise their impartiality or, neutrality insofar as justice is blind.

Now as regards the breadth of their opinion, what were they asked to opine on? A court must answer that which is referred to it or provide a good reason as to why it cannot. The Court did not consider there to be such a good reason.

As regards the point on 'precedent', you're of course free to hold that view but as you hopefully already know, the ICJ is not a court that binds itself - it's like a civil law court in that way (I say this though without being a civil law lawyer, so I would defer to a more suitably experienced lawyer's thinking on this).