Just for starters, fact that the change will in fact give users worse performance than existing extensions like ublock origin provide, because ad blockers under the new scheme will be less effective and the performance impact of ads that get through will MORE than offset any supposed performance gains of the declarative API. It is technologically impossible to create a state of the art adblocker with that declarative API. It's complete trash and Google knows it.

Do yourself a favor and go look up what gorhill has written about the matter. To say that the messaging coming out of google about this change has been intellectually bankrupt is putting it too nicely.