Isn't this incident a case study in how immutable smart contracts are exactly what you don't want in a trustworthy financial system?

The stolen USDT will likely be returned because Tether can do manual freezes like a traditional financial institution.

Where code is law the funds are just gone.

Like even in your example of the marketplace I don't see the benefits over having a central authority. Who determines who is a student or teacher? Who kicks out bad actors? Who resolves disputed transactions?