I agree that fully redundant & separate infrastructure is unrealistic. I'm also not saying you can be 100% prepared. My point is that you can improve your posture.
What you can do is to have a sandbox environment where you periodically do a full setup exercise from a prepper disk. Conceptually it's not that different from testing backup recovery (ok, most companies neglect this too, so maybe you have a point :) ).
Problem is, the value of proper recovery procedures and testing those in all aspects only becomes apparent to the bean-counters when things really break. But until they have been in that situation where nothing works for a month, it will always be too expensive, too cumbersome and too resource-hungry to do those preparations.
What you can do is to have a sandbox environment where you periodically do a full setup exercise from a prepper disk. Conceptually it's not that different from testing backup recovery (ok, most companies neglect this too, so maybe you have a point :) ).