Adblock is not piracy from a technical standpoint, it is refusing certain content, while piracy is accessing content.
In my opinion, neither adblocking or piracy is wrong. In money terms, they are not different from not viewing the content. Perhaps it could be argued that it costs money to run, for example, Youtube's servers, so that adblocking is using their server power without compensating them, but most of these discussions tend to be about the creators, and there it's exactly the same. And piracy is definitely not stealing - you're not deleting the content for someone else by copying it!