If the library wanted to get rid of them, they would've quietly removed the books; I suspect they want people to read them before they're removed, hence the "please give this book a chance" marker.
A deprecation marker is a "this will be removed"; these markers are "this will be removed if nobody reads them even with this marker in them".
Without digressing into spy vs spy, I think deprecation warnings (shared with the customer base) are a good thing. It might not be a good thing for sales, but that's not a concern here either. A / B testing: if I see that, then what tells me WTF is going on? (You lose me here anyway, sales.)
Agree on the language lawyering, too. ;-)
Reframing this point: Some good books aren’t borrowed because they’re not discoverable, not because they’re boring.
The library is highlighting a few titles for increased visibility to ask, “would this pique a reader’s interest if they knew about it, or is this generally bad?”
Without this stage, the library would expunge more genuinely interesting titles.
I’ve always kinda felt the role of a library is for recall rather than precision