C++ contracts standardizes what people already do in C++. Where is the complexity in that? It removes the need to write your own implementation because the language provides a standard interoperable one.
An argument can be made that C++26 features like reflection add complexity but I don't follow that argument for contracts.
The quote of Bjarne is a bit out of context. It was made after an hour long talk about the pitfalls and problems of contracts in c++26: https://youtu.be/tzXu5KZGMJk
An argument can be made that C++26 features like reflection add complexity but I don't follow that argument for contracts.