[bscphil]

I don't think anyone denies the performance improvements and other advantages of the Quantum project. The claim is that the transition wasn't handled well, as replacement APIs for the deprecated addon system weren't in place until several releases after Quantum debuted, and several of the more deep-reaching abilities addons had were deprecated completely. This broke many people's workflows, destroying trust.

This also happened a short time after Mozilla previously broke addons with the e10s changes, requiring many (most?) of them to be rewritten.

Basically, people don't trust Mozilla to handle transitions well any more, even when they happen to be worthwhile transitions.