By all means, let us get rid of all of these things.
Prisons existing is not a societal failure. You can't have a society with 330 million people and not have at least 1 murderer who is relentlessly violent, who needs to be physically confined to protect everyone around them. As soon as you have 1 individual like that (which is almost guaranteed by the law of large numbers irrespective of how good that society is), you've already agreed that some kind of prison (whether or not you label it as such) is necessary.
Every large country has some kind of supermax prison, including Scandinavian countries, because it's a simple reality that individuals like the above exist in small numbers.
How many of these people are the Dexter type murderer?
I'm focusing on the part I think we can all agree on and therefore is solvable.
It can be a historical running dark joke - "Sadly <x> still qualified as an improvement." such as slavery technically being a bit better than early human warfare ending in genocide either directly or indirectly (forced out of all territory capable of sustaining themselves).
That doesn't mean we shouldn't try to do better (ones with far better recidivism rates should be a model for one) but given the history it isn't a failing in itself - that would suggest a shift away from widespread killing and mutilating people was a mistake.
So the question becomes how do you reconcile the secretly dark desire to wipe undesirables off the face of the earth forever vs a legal system that says that people do have the right to live normal lives after they've paid their debts to society. There isn't really a viable middle ground here. The current status quo is to just spend ungodly amounts of tax dollars deferring the dilemma to X years in the future. But when the time is up, either you wait for a relapse and go through the whole thing again, or you just accept that society wants undesirables banished and just kill them all all the time to free resources, or you come up with some reasonable reintegration strategy where people are ok living near ex-cons. Most people would probably balk at the idea of unconditional life/death sentences, under some tautological idea of justice. You can see small scale cases where reformed murderers claim to have found god and built families, and whatever. The challenge is that there's a lot of very strong stigma as soon as you leave tight social circles and that's where the relapses often come from.
You may put a rapist in a prison but then they serve their sentence and might go on to become your neighbor, regardless of whether they repent or are willing to rape again. Where do you put them then? Who gets to decide who's unrepentant? You see how the question gets uncomfortable?
I get that you're trying to just imply that some criminals should just rot in prison, but that's exactly the blindsidedness that I was talking about when it comes to discussions about prison systems.
If you scroll elsewhere, you can see I also mentioned that one could spend weeks fruitlessly debating what constitutes a criminal beyond redemption and that that does add extra layers of touchiness when it comes things like capital punishment.
You may not like capital punishment (and I'm neither condemning nor advocating for it), but it is a real punishment framework that addresses tax burden and the problem of discomfort of having to live near a sex offender. Does it have flaws? Absolutely. As you said yourself, justice systems make mistakes. When I said "tautological idea of justice", what I'm deriding is the double standard some people fall into when making an argument that boils down to "killing innocent people is wrong because it cannot be undone" and use that as a differentiator in opinion between capital punishment and long prison sentences, since one can also make the same argument about innocent inmates (the "silver lining" type of argument is usually callously oblivious to the horrors of prison life, as well as stigma, trauma, loss of opportunity and health, etc and the fact that this damage cannot be undone, no matter how much one thinks saying "oops, sorry" is good enough). One can flip the silver lining argument as such: "at least he was put out of his misery quickly". (Again, not advocating for it, just reiterating that side of the debate)
A lot of anti-prison folks will argue that the better option is reintegration, which involves skill development, counseling, etc. This gels well with the vast majority of inmates who are in prison for small crimes. The flaw, of course, is that you can't really proactively stop the odd psychopath. Trade-offs, trade-offs.
Unfortunately the American people voted otherwise. See what Harris was up to in CA. Expect it to be rolled out nationwide. Biden created the laws that made it possible. They are a right pair.