If this change reduces the overall efficacy of advertising on websites, then we'll likely see many independent websites go out of business. Facebook will love this, as it seems like their goal to rub out (yes, I mean this in the mobster sense) the web outside of them.
Maybe we need a compromise?
Have a website somehow "vouch" for the third-party cookies in use on their site by either disclosing them to their users, or letting them present an option/warning to visitors that says "To keep our site financially sustainable, we ask that visitors accept cookies from our advertisers -- to that end, we require cookies to not be blocked to access our content".
I understand why people detest advertising, but it's also part of a commercial ecosystem that keeps the independent web alive and kicking. If we allow the blocking of third-party cookies, we should also give webmasters the power to block access from anyone who is blocking them, and even more, blocking ads on their site. It's only fair.