I hear what you are saying about dead storage. In my case, however, Arq’s ability to detach locations serves my need for cold storage.
I keep multiple copies of local backups, so I have rarely needed to restore files from AWS. (But I routinely do small test restores to insure all is well.)
The bulk of my “cold” data consists of a few decades of paper scanned to PDF. The files and folders of the “EagleFiler-Archive” are static.
I created this backup location specifically so I could detach it from Arq when everything had been scanned. It is no longer a part of my backup procedure, but the software still “remembers” it.
One copy of the data is on my Mac, another on a drive in storage. But should I ever need to recover anything, I can reattach the archive to Arq with a few clicks after entering the encryption password.
There are all kinds of ways to protect your data. The trick is to find one that fits your needs, and periodically test it to insure it is working. This has been working for me.