Assuming the person is a passive consumer with no messages / money exchanged with anyone, it is very hard to prove social harm or damage. Sentences should be proportional to the crime. Treating possession of cp as equivalent of literally raping a child just seems absurd to me. IMO, just for the legal protection of the average citizen, a simple possession should never warrant jail time.
For the record, i'm against any kind of child abuse, and 25 years for an actual abuser would not be a problem.
But...
Should you go to prison for possesing images of an adult being raped? What if you don't even know it's rape? What if the person is underage, but you don't know (looks adult to you)? What about a murder video instead of rape? What if the child porn is digitally created (AI, photoshop, whatever)? What if a murder scene is digitally created (fake bullets, holes+blood made in video editing software)? What if you go to a mainstream porno store, buy a mainsteam professional porno video and you later find out that the actress way a 15yo Traci Lords?
You do in some countries. For instance, knowingly possessing video of the Christchurch massacre is illegal in New Zealand, due to a ruling by NZ’s Chief Censor (yes, that’s the actual title), and punishable by up to 14 years in prison.
