They made a wise decision, but are certain to be criticized for it. The nine justices, six of whom are grandparents, walked the fine line between parents and grandparents rights based on a Washington state law that allows any person, non-relatives as well as grandparents to seek visitation rights with children. The court went into the murky waters of family law with the case. Families have been in transition for the last couple of decades to a point where nuclear families are more often the exception than the rule.
Grandparents can have an incredibly important and positive impact on their grandchildren.
Some parents for a variety of reasons, some reasonable and some not, don't allow their children to see their grandparents. For the children's benefit, parents should have some compelling reasons to reach the decision to keep their children away from the children's grandparents. Those parents, may not feel inclined to share the reasons for their decision with others- including the government and they shouldn't be forced to do so. Presumably parents are making decisions that ensure their children's best welfare and keeping kids away from their grandparents, may in some cases, be in the child's best interest. Despite changes in family composition, parents rights should ultimately win out.