Nor has the marketplace determined that Disney Corp. should be paid in perpetuity, nor even down to the present time, for all derivative works based on the character in “Steamboat Willie”. The latter was decided by political intervention in the marketplace, by passage of a law contrary to the plain spirit of the Constitutional clause granting power to Congress to grant copyrights.
And, the perpetual, inheritable, alienable copyright you advocate cannot be done by the marketplace, but only by state power enforcing a monopoly on behalf of the rightsholder, an exercise of state power, which in the American context is unconstitutional, since Congress is not granted the power to grant exclusive rights to authors and inventors in perpetuity, but only for a limited term.
The creator should have a monopoly on his work, within reason. If he chooses to cede that monopoly to some other power or entity, so be it. Let him use the law as he sees fit. This is one area where paradise will not issue forth. There is nothing unfair in allowing Disney and his agents use of the law to maintain profits from the creative efforts of Mr. Disney for an indefinite period of time, or to be extended as they might argue in court. People who want to make money off of Mickey Mouse can either shove off, pay royalties, or act under the radar with some risk.