That Moses summoned Aaron and his sons to officiate at the dedication of the Tabernacle is understandable, but for what purpose did he call on the elders? We do not find them performing any function whatsoever.
The answer may be found in the he-goat and the calf which the children of Israel offered at the ceremony. According to our sages, the he-goat was to atone for the sale of Joseph, while the calf was to atone for the sin of the golden calf. The sin of the golden calf was due to Israel's desire to replace Moses with some tangible object which would represent the Almighty. Their motivation was laudable, but sincerity of intent alone is not sufficient. Instead of instructing Aaron to follow their directives, they should have approached him in a spirit of inquiry. They ignored Aaron's leadership, with catastrophic results.
Similarly in the case of Joseph's brothers, they had judged Joseph to be a threat to family unity. Their intent was noble, but they refused to submit their ambition to the leadership personified by their father. Likewise the result was the tragic enslavement of our people at the hands of Pharaoh and Egypt. It was therefore to impress on Israel that motivation on its own, without the guidance of leadership, is a recipe for disaster, that Moses called on the elders of Israel to stand at his side during the entire consecration ceremony.
The rabbis tell us that the two sins of the golden calf and the sale of Joseph follow us down through the ages. The sin of the golden calf represents the desire for religious expression, that of the sale of Joseph the desire for the unity of Israel. Both are worthy aspirations, but without submission to rabbinic leadership there is only one result- the fragmentation of the Jewish people.