Patents cover discoveries, which, as a class, are limited, whereas copyrighted works are created, and therefore (in some sense) unlimited.
Or, in other words: a patent can block access to something that is potentially irreplaceable, and that would have been discovered by others, eventually. Donald Duck just wouldn’t exist without Disney.
The goal of copyright is to provide some incentive for creation. At the same time, it limits the distribution of those works and the benefit that brings, an effect called deadweight loss. Those two goals—amount & quality of creation and distribution—are in perpetual conflict, and the limited time is supposed to balance them for maximum benefit. Is death + 70/95 years too long? Yes, defjnitely. I remember seeing something like 15 years being floated as the true optimum, but it’s likely to differ by category. But it’s just as annoying to often see complete ignorance or denial of the basic mechanism (I. e. “Commercial music suxx anyway” or “why should I pay for news”)
(Another item on this scale: trademarks, which are entirely imbued with value by the owner’s exclusive right to use them. They are not time-limited as long as they are used because, to a first approximation, the value of “Levi’s” has nothing to do with the beauty of the word (which one could consider a limited ressource), but depends on the company’s interest in maintaining its status)