There is no stripping of assets.
The natural state of a creative work is to be in the public domain. Authors do not create copyrights; the public creates them (through our servant, the government), with the public benefit in mind. Some works aren't even eligible for copyright at all, because it wouldn't be for the public benefit. When a copyright is granted, it is for a limited period of time, because a perpetual copyright can never be for the public benefit.
Thus, a better way to imagine the situation is this: if the government owns a parcel of public land, such as a small building suitable for a restaurant at a visitor's center in a national park, it can rent the restaurant space to a private business for a period of time. So long as the restaurateur makes his rent and follows other previously agreed upon terms (e.g. compliance with applicable law, signage that complies with the standards set by the park administrators, etc) he is free to profit as much as he can.
But when the lease expires, the restaurateur cannot argue that his business venue has been taken from him, even though it might be a profitable location forever. It was never his to begin with; he just got to use it for a while.
Regarding Mickey Mouse, copyright policy has to ignore subjective assessments of artistic value. What's important is getting as many works as possible created, published, and into the public domain (and as close to the public domain as possible until fully in the public domain). That's how you best serve the public interest.
And if an author argues that his private interest is more important than the public interest, that's all well and good, and I don't have a problem with his self interest (indeed, we're relying on it to motivate him), but why should the public ignore its own collective self interest? As there's no possibility of a copyright without it being granted by the public, authors are not in a strong bargaining position.