It's worth noting that historically that RFC 2109 and RFC 2965 specified that user agents should respect the user's privacy and not allow cross-server cookies. Since browsers have flat out ignored this recommendation since the beginning this never meant anything, and newer RFCs explicitly allow the default. But if we had been a little more prescient this mess could have been avoided.
It's also worth noting that anecdotically, blocking all third party cookies and running an adblocker has not lead to "breaking the web" in my personal use. I can count any issues I encountered on one hand, and I've run this setup for years. It might me that my internet use is weird (I don't believe so) but it makes me feel the consequences for users for this is overblown.
It's not for lack of prescience. Lou Montulli (the guy who created cookies) realized that third-party cookies were being used for tracking and advertising early on and made the decision to not to break them. I think his reasoning [1] has stood up well too.
It's also worth noting that anecdotically, blocking all third party cookies and running an adblocker has not lead to "breaking the web" in my personal use. I can count any issues I encountered on one hand, and I've run this setup for years. It might me that my internet use is weird (I don't believe so) but it makes me feel the consequences for users for this is overblown.