Note that the parent comment says "why should we allow entities to monopolize IP _long after the creators are dead". Reducing copyright length to a more sane level would prevent exactly this: How on earth is arresting and mildly reversing the ceaseless march of extended copyright terms "swinging to the opposite extreme?"
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.
There's no chance Disney will be happy with any solution which involves losing any level of control over any copyright they currently own (or will own in the future).
Although they would, I'm sure, be happy for other people to have to pay to maintain their copyright, making it easier to plagiarise poorer creators.
It also presents another problem: one of the objectives of copyright is to reward innovation. If you created something new, it makes sense to let you profit from it for a time. But if you can profit from it forever, you have no reason to innovate more.
Not innovating more goes against one of the objectives of copyright. It's also bad for the economy, for the people, for everyone. We need innovation.