We are in effect so busy arranging the beach umbrellas per our instructions that we don't notice the approaching tsunami.
Economists focus on what can be easily measured: sales, profits, prices, tax revenues, etc. Since the decay and failure of institutions isn't easily quantified, this decay doesn't register in the realm of economics. Since it isn't measured, it doesn't exist.
But institutional decay and failure is all too real, and it begs the question: how can a society and economy thrive if its core institutions fail?