It's quite simple. Disney and other companies have enough power to influence the law. If you change the law to something more reasonable they will just change it back.
It is extreme in the sense that current copyright extremely favours major companies. Going the opposite way extremely disfavours major companies with IP that spans centuries.
You have to find a compromise so that both companies and everyone else is happy with.
The compromise is simple. Allow copyright extensions indefinitively on an individual basis in exchange for a fee. If mickeymouse is profitable to disney then let them have it. They will get it at any cost anyway and destroy a lot of things in the process. Sacrificing perpetually profitable IP is a small cost in exchange for all the works that are no longer profitable which is probably more than 99% of all works.