It blocks some of them, usually the most basic. I also seem to remember that by not answering those prompts (and hiding them instead), you actually consent until you decline.

It absolutely can't block the more advanced, sometimes multi-stage prompts Google, Youtube, and many newspapers use. Consent-o-Matic actually goes through those prompts and declines the maximum possible amount of tracking, while consenting to the necessary options required to make the site work.