I can’t tell if you’re trolling or not. The range of “fancy” restaurants is nearly as wide as the variety of food itself.
Over-priced mediocre steakhouses? Yeah, you’re probably right. Alinea or Franch Laundry? You’re crazy.
I absolutely go to fancy restaurants to find food I can’t buy or cook myself. A professional kitchen has ingredients, equipment, and techniques that I don’t.
I think your premise really has nothing to do with the restaurants themselves and is mostly a complaint about the existence of the super-rich and the problem of conspicuous consumption. I don’t disagree with you there, but you’re choosing a weird hill to plant your flag on.