You're right, which makes this situation tricky to reverse. But the least we could do is stop continually extending and strengthening copyright termsI'm entirely with you on almost all of this. I see no economic or moral argument for granting the longer-than-human-lifetimes durations of copyright that we have in most places today.
There is no good argument that I can see not to reduce the guaranteed period of exclusivity for new works to something much more reasonable, still enough to provide a robust economic incentive to create and share new work in the first place (which I note could be very different depending on the nature of each work, its creator(s) and its intended audience) but not completely disproportionate to that goal.
For the record, I also see few good arguments against retrospectively reversing copyright term extensions that apply to works that were originally created and distributed when lesser incentives were in effect, and none at all if the rights haven't been transferred since such an extension was introduced in law.
I'm in two minds on the theft question. Yes, intellectual and physical property are different things and have different characteristics, but ultimately both are artificial legal constructs anyway, as are the rights to control them that the law provides. Copyright infringement very often is done in a way that ultimately denies the rightsholder real money or other compensation to which they would have been entitled had the same actions been taken in a legal way, and in that situation I see little moral distinction between ripping the work without paying the money or stealing the same amount of money from someone's bank account after the fact.
Clearly not all copyright infringement falls into this category, because of the usual (reasonable) arguments that not every illegal copy represents a lost sale, etc. However, it has been my experience that most of the time when people start raising the "copyright infringement is not theft" point in an argument, they're really attempting to use sophistry to shift the argument away from what was otherwise a straightforward case of them knowingly breaking the law and ripping someone off, and which is in fact still exactly that regardless of what label is used.