Maybe C++ overthought the generality of the feature and under-delivered on the MVP (a common committee failure mode). Two keywords such as "always-enforce" and "build-configurable" for assertions would have covered the vast majority of what people wanted from contracts.

Also from a procedural perspective the technical committee was wrong. It is supposed to send drafts to DIS when there is consensus. They did it based an a plenary vote. That is not what consensus is, and also not how ISO defines it. Consensus is the absence of sustained opposition. Contracts never had consensus, DIS simply responded to that procedural snafu.