Everybody saying declarativeNetRequest is sufficient and Apple's Safari content blocking works perfectly fine is entirely missing the point. Both of those state

Everybody saying declarativeNetRequest is sufficient and Apple's Safari content blocking works perfectly fine is entirely missing the point. Both of those statements are true enough, _for right now_. Losing the ability to modify content in this manner means adblockers can't compete in the arms race against advertisers. Anti-adblock scripts running locally with randomly-generated names will render this sort of declarative content blocking ineffective.