I think perhaps the missing piece here is the suggestion that the status quo is cheaper in the short term but (IIUC you're suggesting) more expensive in the long term. Of course the problem is convincing current management first of this fact followed by why that should matter to them.

But amusingly this all seems to be rapidly changing with the advent of AI agents since they don't work all that well without a clear spec and thorough documentation (and likely comprehensive tests as well).