Cookie handling doesn't need to be this complicated. A huge part of the solution would be if third-party cookies simply stopped working by default. Sure, there are a lot of big corporate interests preventing this from happening, but if you think about it there is really almost no legitimate use for them that benefits the users.
On a related note, Chrome has a setting that simply kills all the cookies when the browser is shut down. The price is having to log into everything all over again, but it's not that much of a hassle in exchange for a clean plate every morning.
Firefox has the same setting, the problem is that many of us don't want to restart the browser every morning. Using suspension, my browser sessions tend to last more than a month.
On a related note, Chrome has a setting that simply kills all the cookies when the browser is shut down. The price is having to log into everything all over again, but it's not that much of a hassle in exchange for a clean plate every morning.