The potential loss of authenticity and spontaneity ought to concern us, but we should not let it become an excuse for inaction. Ephemera can also become the reason for actually getting things done. For example, Barcelona made 30 years of infrastructure investment in 6 years when it was selected as the city for the Olympics. It's often suggested that these hallmark events offer the opportunity to extract considerable funds from other levels of government. Work is not the highest end of life.
Festivity is an end in itself.
It is not instrumental. And ephemera allow fantasy and social criticism. There are a series of values that are in conflict. These ephemera are signs of public life that we like. But there are other sets of values that are running simultaneously.