If I can recognize an ad, I can construct JavaScript that can recognize that ad too. The current extension APIs let me inject that JavaScript, while the declarative ad blocking APIs do not.
This is a constant arms race, as anyone who’s looked at Facebook’s DOM knows, and if you’re successful it pushes to the end state I mentioned of ads becoming very similar to the content. The companies which depend on ad revenue aren’t going to go out of business voluntarily and many of them will find alternative paths to those ad dollars.
